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                                                                     EXHIBIT 3.3

                            CERTIFICATE OF FORMATION

                                       OF

                               NRP (OPERATING) LLC


         This Certificate of Formation, dated April 17, 2002, has been duly
executed and is filed pursuant to Sections 18-201 and 18-204 of the Delaware
Limited Liability Company Act (the "Act") to form a limited liability company
(the "Company") under the Act.

         1. NAME. The name of the Company is:

            NRP (Operating) LLC

         2. REGISTERED OFFICE; REGISTERED AGENT. The address of the registered
office required to be maintained by Section 18-104 of the Act is:

            Corporation Trust Center
            1209 Orange Street
            Wilmington, Delaware  19801.

         The name and the address of the registered agent for service of process
required to be maintained by Section 18-104 of the Act are:

            The Corporation Trust Company
            Corporation Trust Center
            1209 Orange Street
            Wilmington, Delaware  19801.

         EXECUTED as of the date written first above.



                                                  By: /s/ DWIGHT L. DUNLAP
                                                      ------------------------
                                                  Name:   Dwight L. Dunlap
                                                          Authorized Person


