Exhibit 3.19

                                                                       Exhibit A

                               SVM of Texas, Inc.

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                                     BY-LAWS

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                                    ARTICLE I

                                     OFFICES

                  Section 1. The registered office shall be located in Dallas,
Texas.

                  Section 2. The corporation may also have offices at such other
places both within and without the State of Texas as the board of directors may
from time to time determine or the business of the corporation may require.

                                   ARTICLE II
                         ANNUAL MEETINGS OF SHAREHOLDERS

                  Section 1. All meetings of shareholders for the election of
directors shall be held in Dallas, State of Texas, at such place as may be fixed
from time to time by the board of directors. Said meetings may also be held at
such other place either within or without the State of Texas as shall be
designated from time to time by the board of directors and stated in the notice
of the meeting.

                  Section 2.  Annual meetings of shareholders commencing
with the year 1984 shall be held on the first Monday of October,


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if not a legal holiday, and if a legal holiday, then on the next secular day
following, at which they shall elect by a plurality vote a board of directors,
and transact such other business as may properly be brought before the meeting.

                  Section 3. Written or printed notice of the annual meeting
stating the place, day and hour of the meeting shall be delivered not less than
ten, nor more than fifty, days before the date of the meeting, either personally
or by mail, by or at the direction of the president, the secretary or the
officer or persons calling the meeting, to each shareholder of record entitled
to vote at such meeting.

                                   ARTICLE III
                        SPECIAL MEETINGS OF SHAREHOLDERS

                  Section 1. Special meetings of shareholders for any purpose
other than the election of directors may be held at such time and place within
or without the State of Texas as shall be stated in the notice of the meeting or
in a duly executed waiver of notice thereof.

                  Section 2. Special meetings of the shareholders for any
purpose or purposes, unless otherwise prescribed by statute or by the articles
of incorporation, may be called by the president, the board of directors, or the
holders of not less


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than one-tenth of all of the shares entitled to vote at the meeting.

                  Section 3. Written or printed notice of a special meeting
stating the place, day and hour of the meeting and the purpose or purposes for
which the meeting is called, shall be delivered not less than ten, nor more than
fifty, days before the date of the meeting, either personally or by mail, by or
at the direction of the president, the secretary, or the officer or persons
calling the meeting, to each shareholder of record entitled to vote at such
meeting.

                  Section 4. The business transacted at any special meeting of
shareholders shall be limited to the purposes stated in the notice.

                                   ARTICLE IV
                           QUORUM AND VOTING OF STOCK

                  Section 1. The holders of a majority of the shares of stock
issued and outstanding and entitled to vote, represented in person or by proxy,
shall constitute a quorum at all meetings of shareholders for the transaction of
business except as otherwise provided by statute or by the articles of
incorporation. If, however, such quorum shall not be present or represented at
any meeting of the shareholders, the shareholders present in person


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or represented by proxy shall have power to adjourn the meeting from time to
time, without notice other than announcement at the meeting, until a quorum
shall be present or represented. At such adjourned meeting at which a quorum
shall be present or represented any business may be transacted which might have
been transacted at the meeting as originally notified.

                  Section 2. If a quorum is present, the affirmative vote of a
majority of the shares of stock represented at the meeting shall be the act of
the shareholders unless the vote of a greater number of shares of stock is
required by law or the articles of incorporation.

                  Section 3. Each outstanding share of stock, having voting
power, shall be entitled to one vote on each matter submitted to a vote at a
meeting of shareholders. A shareholder may vote either in person or by proxy
executed in writing by the shareholder or by his duly authorized
attorney-in-fact.

                  In all elections for directors every shareholder, entitled to
vote, shall have the right to vote, in person or by proxy, the number of shares
of stock owned by him, for as many persons as there are directors to be elected.

                  Section 4. Any action required to be taken at a meeting of the
shareholders may be taken without a meeting if a consent in writing, setting
forth the action so taken, shall be


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signed by all of the shareholders entitled to vote with respect to the subject
matter thereof.

                                    ARTICLE V

                                    DIRECTORS

                  Section 1. The number of directors shall be three. Directors
need not be residents of the State of Texas nor shareholders of the corporation.
The directors, other than the first board of directors, shall be elected at the
annual meeting of the shareholders, and each director elected shall serve until
the next succeeding annual meeting and until his board of directors shall hold
office until the first annual meeting of shareholders.

                  Section 2.  Any vacancy occurring in the board of directors
may be filled by the affirmative vote of a majority of the remaining directors
though less than a quorum of the board of directors. A director elected to fill
a vacancy shall be elected for the unexpired portion of the term of his
predecessor in office.

                  Any directorship to be filled by reason of an increase in the
number of directors shall be filled by election at an annual meeting or at a
special meeting of shareholders called for that purpose. A director elected to
fill a newly created

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directorship shall serve until the next succeeding annual meeting of
shareholders and until his successor shall have been elected and qualified.

                  Section 3. The business affairs of the corporation shall be
managed by its board of directors which may exercise all such powers of the
corporation and do all such lawful acts and things as are not by statute or by
the articles of incorporation or by these by-laws directed or required to be
exercised or done by the shareholders.

                  Section 4. The directors may keep the books of the
corporation, except such as are required by law to be kept within the state,
outside of the State of Texas, at such place or places as they may from time to
time determine.

                  Section 5. The board of directors, by the affirmative vote of
a majority of the directors then in office, and irrespective of any personal
interest of any of its members, shall have authority to establish reasonable
compensation of all directors for services to the corporation as directors,
officers or otherwise.

                                   ARTICLE VI
                       MEETINGS OF THE BOARD OF DIRECTORS


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                  Section 1. Meetings of the board of directors, regular or
special, may be held either within or without the State of Texas.

                  Section 2. The first meeting of each newly elected board of
directors shall be held at such time and place as shall be fixed by the vote of
the shareholders at the annual meeting and no notice of such meeting shall be
necessary to the newly elected directors in order legally to constitute the
meeting, provided a quorum shall be present, or it may convene at such place and
time as shall be fixed by the consent in writing of all the directors.

                  Section 3. Regular meetings of the board of directors may be
held upon such notice, or without notice, and at such time and at such place as
shall from time to time be determined by the board.

                  Section 4. Special meetings of the board of directors may be
called by the president on two days' notice to each director, either personally
or by mail or by telegram; special meetings shall be called by the president or
secretary in like manner and on like notice on the written request of two
directors.

                  Section 5. Attendance of a director at any meeting shall
constitute a waiver of notice of such meeting, except where


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a director attends for the express purpose of objecting to the transaction of
any business because the meeting is not lawfully called or convened. Neither the
business to be transacted at, nor the purpose of, any regular or special meeting
of the board of directors need by specified in the notice or waiver of notice of
such meeting.

                  Section 6. Two of the directors shall constitute a quorum for
the transaction of business unless a greater number is required by law or by the
articles of incorporation. The act of a majority of the directors present at any
meeting at which a quorum is present shall be the act of the board of directors,
unless the act of a greater number is required by statute or by the articles of
incorporation. If a quorum shall not be present at any meeting of directors, the
directors present thereat may adjourn the meeting from time to time, without
notice other than announcement at the meeting, until a quorum shall be present.

                  Section 7. Unless otherwise restricted by the articles of
incorporation or these by-laws, any action required or permitted to be taken at
any meeting of the board of directors or of any committee thereof may be taken
without a meeting, if all members of the board or committee, as the case may be,
consent thereto in writing which shall set forth the action taken and be



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signed by all members of the board of directors or of the committee as the case
may be.

                                   ARTICLE VII

                             COMMITTEES OF DIRECTORS

                  Section 1. The board of directors, by resolution adopted by a
majority of the full board of directors, may designate from among its members an
executive committee and one or more other committees, each of which, to the
extent provided in the resolution, shall have and may exercise all of the
authority of the board of directors, except that no such committee shall have
the authority of the board of directors in reference to amending the articles of
incorporation, approving a plan of merger or consolidation, recommending to the
shareholders the sale, lease or exchange of all or substantially all of the
property and assets of the corporation otherwise than in the usual and regular
course of its business, recommending to the shareholders a voluntary dissolution
of the corporation or a revocation thereof, amending, altering, or


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repealing the by-laws of the corporation or adopting new by-laws for the
corporation, filling vacancies in the board of directors or any committee,
electing or removing officers or members of any committee, fixing the
compensation of any member of a committee, or altering or repealing any
resolution of the board of directors which by its terms provides that it shall
not be so amendable or repealable; and, unless the resolution expressly so
provides, no committee shall have the power or authority to declare a dividend
or to authorize the issuance of shares of the corporation.

                                  ARTICLE VIII

                                     NOTICES

                  Section 1. Whenever, under the provisions of the statutes or
of the articles of incorporation or of these by-laws, notice is required to be
given to any director or shareholder, it shall not be construed to mean personal
notice, but such notice may be given in writing, by mail, addressed to such
director or shareholder, at his address as it appears on the records of the
corporation, with postage thereon paid, and such notice shall be deemed to be
given at the time when the same shall be deposited in the United States mail.
Notice to directors may also be given by telegram.

                  Section 2. Whenever any notice whatever is required to be
given under the provisions of the statutes or under the pro visions of the
articles of incorporation or these by-laws, a waiver thereof in writing signed
by the person or persons en-

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titled to such notice, whether before or after the time stated therein, shall be
deemed equivalent to the giving of such notice.

                                   ARTICLE IX

                                    OFFICERS

                  Section 1. The officers of the corporation shall be chosen by
the board of directors and shall be a president and a secretary. The board of
directors may also choose one or more vice presidents, a treasurer, and one or
more assistant secretaries and assistant treasurers.

                  Section 2. The board of directors at its first meeting after
each annual meeting of shareholders shall choose the officers, none of whom need
be a member of the board.

                  Section 3. The board of directors may appoint such other
officers and agents as it shall deem necessary who shall hold their offices for
such terms and shall exercise such powers and perform such duties as shall be
determined from time to time by the board of directors.

                  Section 4. The salaries of all officers and agents of the
corporation shall be fixed by the board of directors.

                  Section 5. The officers of the corporation shall hold office
until their successors are chosen and qualify. Any officer elected or appointed
by the board of directors may be removed at


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any time by the affirmative vote of a majority of the board of directors. Any
vacancy occurring in any office of the corporation shall be filled by the board
of directors.

                                  THE PRESIDENT

                  Section 6. The president shall be the chief operating officer
of the corporation, shall have general and active manage ment of the day to day
business of the corporation and shall see that all orders and resolutions of the
board of directors are carried into effect.

                  Section 7. He shall execute bonds, mortgages and other
contracts requiring a seal, under the seal of the corporation, except where
required or permitted by law to be otherwise signed and executed and except
where the signing and execution thereof shall be expressly delegated by the
board of directors to some other officer or agent of the corporation.

                               THE VICE PRESIDENTS

                  Section 8. The vice president, if any, or if there shall be
more than one, the vice presidents in the order determined by the board of
directors, shall, in the absence or disability of the president, perform the
duties and exercise the powers of the president and shall perform such other
duties and have such powers as the board of directors may from time to time
prescribe.

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                     THE SECRETARY AND ASSISTANT SECRETARIES

                  Section 9.  The secretary shall attend all meetings of the
board of directors and all meetings of the shareholders and record all the
proceedings of the meetings of the corporation and of the board of directors in
a book to be kept for that purpose and shall perform like duties for the
standing committees when required. He shall give, or cause to be given, notice
of all meetings of the shareholders and special meetings of the board of
directors, and shall perform such other duties as may be pre scribed by the
board of directors or president, under whose supervision he shall be. He shall
have custody of the corporate seal of the corporation and he, or an assistant
secretary, shall have authority to affix the same to any instrument requiring it
and when so affixed, it may be attested by his signature or by the signature of
such assistant secretary. The board of directors may give general authority to
any other officer to affix the seal of the corporation and to attest the
affixing by his signature.

                  Section 10. The assistant secretary, if any, or if there be
more than one, the assistant secretaries in the order determined by the board of
directors, shall, in the absence or disability of the secretary, perform the
duties and exercise the powers of the secretary and shall perform such other
duties and


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have such other powers as the board of directors may from time to time
prescribe.

                     THE TREASURER AND ASSISTANT TREASURERS

                  Section 11.  The treasurer shall have the custody of the
corporate funds and securities and shall keep full and accurate accounts of
receipts and disbursements in books belonging to the corporation and shall
deposit all moneys and other valuable effects in the name and to the credit of
the corporation in such depositories as may be designated by the board of
directors.

                  Section 12. He shall disburse the funds of the corporation as
may be ordered by the board of directors, taking proper vouchers for such
disbursements, and shall render to the president and the board of directors, at
its regular meetings, or when the board of directors so requires, an account of
all his transactions as treasurer and of the financial condition of the
corporation.

                  Section 13. If required by the board of directors, he shall
give the corporation a bond in such sum and with such surety or sureties as
shall be satisfactory to the board of directors for the faithful performance of
the duties of his office and for the restoration to the corporation, in case of
his death, resignation, retirement or removal from office, of all


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books, papers, vouchers, money and other property of whatever kind in his
possession or under his control belonging to the corporation.

                  Section 14. The assistant treasurer, if any, or, if there
shall be more than one, the assistant treasurers in the order determined by the
board of directors, shall, in the absence or disability of the treasurer,
perform the duties and exercise the powers of the treasurer and shall perform
such other duties and have such other powers as the board of directors may from
time to time prescribe.

                                    ARTICLE X

                             CERTIFICATES FOR SHARES

                  Section 1. The shares of the corporation shall be represented
by certificates signed by the president or a vice president and the secretary or
assistant secretary of the corpor ation, and may be sealed with the seal of the
corporation or a facsimile thereof.

                  When the corporation is authorized to issue shares of more
than one class there shall be set forth upon the face or back of the
certificate, or the certificate shall have a statement that the corporation will
furnish to any shareholder upon request and without charge, a full statement of
the designations, preferences, limitations and relative rights of the


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shares of each class authorized to be issued and the corporation will furnish a
copy of such statement to the record holder of the certificate without charge on
written request to the corporation at its principal place of business or
registered office. Every certificate shall have noted thereon any information
required to be set forth by the Texas Business Corporation Act and such
information shall be set forth in the manner provided in said Act.

                  Section 2. The signatures of the officers of the corporation
upon a certificate may be facsimiles if the certificate is countersigned by a
transfer agent, or registered by a registrar, other than the corporation itself
or an employee of the corporation. In case any officer who has signed or whose
facsimile signature has been placed upon such certificate shall have ceased to
be such officer before such certificate is issued, it may be issued by the
corporation with the same effect as if he were such officer at the date of its
issue.

                                LOST CERTIFICATES

                  Section 3. The board of directors may direct a new certificate
to be issued in place of any certificate theretofore issued by the corporation
alleged to have been lost or destroyed. When authorizing such issue of a new
certificate, the board of directors, in its discretion and as a condition
precedent to the


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issuance thereof, may prescribe such terms and conditions as it deems expedient,
and may require such indemnities as it deems adequate, to protect the
corporation from any claim that may be made against it with respect to any such
certificate alleged to have been lost or destroyed.

                               TRANSFER OF SHARES

                  Section 4. Upon surrender to the corporation or the transfer
agent of the corporation of a certificate representing shares duly endorsed or
accompanied by proper evidence of succession, assignment or authority to
transfer, a new certificate shall be issued to the person entitled thereto, and
the old certificate cancelled and the transaction recorded upon the books of the
corporation.

                            CLOSING OF TRANSFER BOOKS

                  Section 5. For the purpose of determining shareholders
entitled to notice of or to vote at any meeting of shareholders, or any
adjournment thereof or entitled to receive payment of any dividend, or in order
to make a determination of shareholders for any other proper purpose, the board
of directors may provide that the stock transfer books shall be closed for a
stated period but not to exceed, in any case, fifty days. If the stock transfer
books shall be closed for the purpose of determining shareholders entitled to
notice of or to vote at a meeting of shareholders,


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such books shall be closed for at least ten days immediately preceding such
meeting. In lieu of closing the stock transfer books, the board of directors may
fix in advance a date as the record date for any such determination o f
shareholders, such date in any case to be not more than fifty days and, in case
of a meeting of shareholders, not less than ten days prior to the date an which
the particular action, requiring such determination of shareholders, is to be
taken. If the stock transfer books are not closed and no record date is fixed
for the determination of shareholders entitled to notice of or to vote at a
meeting of shareholders, or shareholders entitled to receive payment of a
dividend, the date on which notice of the meeting is mailed or the date on which
the resolution of the board of directors declaring such dividend is adopted, as
the case may be, shall be the record date for such determination of shareholders
entitled to vote at any meeting of shareholders has been made as provided in
this section, such determination shall apply to any adjournment thereof.

                             REGISTERED SHAREHOLDERS

                  Section 6. The corporation shall be entitled to recognize the
exclusive right of a person registered on its books as the owner of shares to
receive dividends, and to vote as such owner, and to hold liable for calls and
assessments a person


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registered on its books as the owner of shares, and shall not be bound to
recognize any equitable or other claim to or interest in such share or shares on
the part of any other person, whether or not it shall have express or other
notice thereof, except as otherwise provided by the laws of Texas.

                              LIST OF SHAREHOLDERS

                  Section 7. The officer or agent having charge of the transfer
books for shares shall make, at least ten days before each meeting of
shareholders, a complete list of the shareholders entitled to vote at such
meeting, arranged in alphabetical order, with the address of each and the number
of shares held by each, which list, for a period of ten days prior to such
meeting, shall be kept on file at the registered office of the corporation and
shall be subject to inspection by any shareholder at any time during usual
business hours. Such list shall also be produced and kept open at the time and
place of the meeting and shall be subject to the inspection of any shareholder
during the whole time of the meeting. The original share ledger or transfer
book, or a duplicate thereof, shall be prima facie evidence as to who are the
shareholders entitled to examine such list or share ledger or transfer book or
to vote at any meeting of the share holders.

                                   ARTICLE XI


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                         GENERAL PROVISIONS - DIVIDENDS

                  Section 1. Subject to the provisions of the articles of
incorporation relating thereto, if any, dividends may be de clared by the board
of directors at any regular or special meeting, pursuant to law. Dividends may
be paid in cash, in property or in shares of the capital stock, subject to any
pro visions of the articles of incorporation.

                  Section 2. Before payment of any dividend, there may be set
aside out of any funds of the corporation available for dividends such sum or
sums as the directors from time to time, in their absolute discretion, think
proper as a reserve fund to meet contingencies, or for equalizing dividends, or
for repairing or maintaining any property of the corporation, or for such other
purpose as the directors shall think conducive to the interest of the
corporation, and the directors may modify or abolish any such reserve in the
manner in which it was created.

                                     CHECKS

                  Section 3. All checks or demands for money and notes of the
corporation shall be signed by such officer or officers or such other person or
persons as the board of directors may from time to time designate.

                                   FISCAL YEAR


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                  Section 4. The fiscal year of the corporation shall be fixed
by resolution of the board of directors.

                                      SEAL

                  Section 5. The corporate seal shall have inscribed thereon the
name of the corporation, the year of its organization and the words "Corporate
Seal, Texas". The seal may be used by causing it or a facsimile thereof to be
impressed or affixed or in any manner reproduced.

                                   ARTICLE XII

                                   AMENDMENTS

                  Section 1. These by-laws may be altered, amended, or repealed
or new by-laws may be adopted by the affirmative vote of a majority of the board
of directors at any regular or special meeting of the board subject to repeal or
change at any regular or special meeting of shareholders at which a quorum is
present or represented, by the affirmative vote of a majority of the stock
entitled to vote, provided notice of the proposed repeal or change be contained
in the notice of such meeting.

                  Section 2. These by-laws may be altered, amended or repealed
or new by-laws may be adopted at any regular or special meeting of shareholders
at which a quorum is present or represented, by the affirmative vote of a
majority of the stock



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entitled to vote, provided notice of the proposed alteration, amendment or
repeal be contained in the notice of such meeting.