SUPPLEMENT NO. 4 DATEDAUGUST 14, 1998 TO PROSPECTUS DATED OCTOBER 6, 1997 RELATING TO $80,000,000 6 1/4% CONVERTIBLE SUBORDINATED DEBENTURES DUE 2004 INTEREST PAYABLE FEBRUARY 1 AND AUGUST 1 AND SHARES OF COMMON STOCK ISSUABLE UPON CONVERSION THEREOF All capitalized terms used but not defined herein shall have the meanings set forth in the Prospectus dated October 10, 1997, as previously supplemented (the "Prospectus"), forming a part of the Registration Statement on Form S-3 (Registration No. 333-35827). Any cross references in this Supplement refer to portions of the Prospectus. The purpose of this Supplement is to provide additional information regarding the Selling Securityholders. In addition to the Selling Securityholders named in the Prospectus, the following table sets forth the name of each additional Selling Securityholder and relationship, if any, with the Company and (i) the amount of Debentures owned by each additional Selling Securityholder as of August 14, 1998 (subject to the qualification set forth below), (ii) the maximum amount of Debentures which may be offered for the account of such additional Selling Securityholder under the Prospectus, (iii) the amount of Common Stock owned by each additional Selling Securityholder as of August 14, 1998, and (iv) the maximum amount of Common Stock which may be offered for the account of such Selling Securityholder under the Prospectus. Name of Selling Securityholder Principal Amount Principal Amount Shares of Shares of Common of Debentures Owned of Debentures Common Stock Stock Offered Hereby (2) Offered Hereby Owned Prior to Offering(1) Alpine Associates............ 1,500,000 1,500,000 88,889 88,889 Offshore Strategies LTD(4)... 1,220,000 945,000 72,296 56,000 Laterman Strategies 90s LLC(3) 286,600 366,000 16,984 21,689 First Delta Securities....... 300,000 300,000 17,777 17,777 Laterman and Company......... 189,000 189,000 11,200 11,200 Total........................ $3,495,600 $3,300,000 N/A 195,555 ========== ========== === ======= - ----------------------- (1) Includes the shares of Common Stock into which the Debentures held by such Selling Securityholder are convertible at the initial conversion price. The conversion price and the number of shares of Common Stock issuable upon conversion of the Debentures are subject to adjustment under certain circumstances. See "Description of Debentures - Conversion Rights." Accordingly, the number of shares of Common Stock issuable upon conversion of the Debentures may increase or decrease from time to time. (2) Assumes conversion into Common Stock of the full amount of Debentures held by such Selling Securityholder at the initial conversion price. The conversion price and the number of shares of Common Stock issuable upon conversion of the Debentures are subject to adjustment under certain circumstances. See "Description of Debentures - Conversion Rights." Accordingly, the number of shares of Common Stock issuable upon conversion of the Debentures may increase or decrease from time to time. Fractional shares will not be issued upon conversion of the Debentures; rather, cash will be paid in lieu of fractional shares, if any. (3) Includes $250,000 aggregate principal amount of freely tradable Debentures. (4) Includes $275,000 aggregate principal amount of freely tradable Debentures. Because the Selling Securityholders may, pursuant to this Prospectus, offer all or some portion of the Debentures and Common Stock they presently hold or, with respect to Common Stock, have the right to acquire upon conversion of such Debentures, no estimate can be given as to the amount of the Debentures and Common Stock that will be held by the Selling Securityholders upon termination of any such sales. In addition, the Selling Securityholders identified above may have sold, transferred or otherwise disposed of all or a portion of their Debentures and Common Stock since the date on which they provided the information regarding their Debentures and Common Stock, in transactions exempt from the registration requirements of the Securities Act of 1933. See "Plan of Distribution." The Company may from time to time, in accordance with the Registration Rights Agreement, include additional Selling Securityholders in future supplements to the Prospectus. Except as described above, none of the Selling Securityholders listed above had any material relationship with the Company other than as a result of ownership of the Debentures, within the three-year period ending on the date of this Prospectus.