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                                                                    EXHIBIT 3.31


                            CERTIFICATE OF FORMATION
                                       OF
                             WOOD LICENSE CO., LLC

                                      NAME

         The name of the limited liability corporation is WOOD License Co.,
LLC.

                          REGISTERED AGENT AND OFFICE

         The address of the initial registered office of this corporation is
1013 Centre Road, Wilmington, Delaware, 19805; and the name of the registered
agent of the corporation in the State of Delaware is the Corporation Service
Company.

Dated: January 23, 1998
                                                --------------------------------
                                                          Gayle C. Toney