system: You are a contract-analysis assistant performing a span-extraction task. You are given an excerpt from a commercial contract and the name of a clause type to locate within it.

Return the exact text of the requested clause, copied verbatim from the excerpt — identical wording and punctuation, with no paraphrasing, summarising, explanation, or added commentary.

The excerpt is one window of a much longer contract and often will not contain the requested clause. If the requested clause does not appear in this excerpt, respond with exactly: Not found.

Output only the extracted clause text, or the exact string `Not found.` — nothing else.

user: Contract excerpt:
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shall substitute for the prior version within two days after receipt thereof. PaperExchange shall have final approval over all PaperExchange Links on Pulp and Paper Online. 6.5. Except for the express rights granted to PaperExchange under this Agreement, PaperExchange acknowledges and agrees that the Intellectual Property of VerticalNet is and shall remain the sole property of VerticalNet and nothing in this Agreement shall confer in PaperExchange any right of ownership or license rights in VerticalNet's Intellectual Property. In addition, PaperExchange shall not now or in the future contest the validity of VerticalNet's Intellectual Property. 6.6. Except for the express rights granted to VerticalNet under this Agreement, VerticalNet acknowledges and agrees that the Intellectual Property of PaperExchange is and shall remain the sole property of PaperExchange and nothing in this Agreement shall confer in VerticalNet any right of ownership or license rights in PaperExchange's Intellectual Property. In addition, VerticalNet shall not now or in the future contest the validity of PaperExchange's Intellectual Property. 6.7. PaperExchange agrees to use the VerticalNet Marks in accordance with the terms of this Agreement and with good trademark practices including, but not limited to, protecting the value of the goodwill residing in such Intellectual Property. 6.8. VerticalNet agrees to use the PaperExchange Marks in accordance with the terms of this Agreement and with good trademark practices including, but not limited to, protecting the value of the goodwill residing in such Intellectual Property. 6.9. Except as set forth in Sections 4.3 [Non-Competition] and 5.8 [Non-Competition], nothing in this Agreement shall be construed as preventing either party from developing other co-branded versions of its materials, data, information and content. 10 7. COMMERCIAL TERMS 7.1. Co-Branded Sites. 7.1.1. Co-Branded Career Center. VerticalNet will pay PaperExchange ***** of the Career Center Net Revenue. ."Career Center Net Revenue" shall mean the (a) listing fees related to the Co-Branded Career Center and any other VerticalNet Site on which the listings are posted, (b) Co-Branded Career Center e-commerce revenue and (c) other Co-Branded Career Center revenue, in each case under the preceding clauses (a), (b) and (c), to the extent derived during the Term from PaperExchange or the PaperExchange Content provided to VerticalNet by PaperExchange pursuant to this Agreement, or as otherwise mutually agreed upon by the parties, less (i) credits for claims, allowances, retroactive price reductions or returned goods, and (ii) sales, excise, use, value-added and other similar taxes (excluding income taxes) actually paid. 7.1.2. Co-Branded Equipment Listings. VerticalNet will pay PaperExchange ***** of the Equipment Listings Net Revenue. "Equipment Listings Net Revenue" shall mean the (a) listing fees related to Co-Branded Equipment Listings and any other VerticalNet Site on which the listings are posted, (b) Co-Branded Equipment Listings e-commerce revenue and (c) other Co-Branded Equipment Listings revenue, in each case under the preceding clauses (a), (b) and (c), to the extent derived during the Term from PaperExchange or the PaperExchange Content provided to VerticalNet by PaperExchange pursuant to this Agreement, or as otherwise mutually agreed upon by the parties, less (i) credits for claims, allowances, retroactive price reductions or returned goods, and (ii) sales, excise, use, value-added and other similar taxes (excluding income taxes) actually paid. 7.1.3. Review of Payments. VerticalNet and PaperExchange will conduct a good faith review of the payments generated under Sections 7.1.1 [Co-Branded Career Center] and Source: PAPEREXCHANGE COM INC, S-1/A, 3/22/2000 7.1.2 [Co-Branded Equipment Listings] no later than six months after the Effective Date and may mutually agree, subject to Section 13.6 [Amendment or Modification], to amend Sections 7.1.1 [Co-Branded Career Center] and/or 7.1.2 [Co-Branded Equipment Listings] at that time. If VerticalNet and PaperExchange are unable to reasonably agree on whether or how to amend Section 7.1.2 [Co-Branded Equipment Listings], either party shall have the right to immediately terminate the rights and obligations of the parties under Sections 2 and 7.1.2 [Co-Branded Equipment Listings] with respect to the Co-Branded Equipment Listings and PaperExchange Equipment Content; provided, however, that all other rights and obligations under this Agreement (including the rights and obligations of the parties under Sections 4.3 [Non-Competition] and 5.8 [Non-Competition]) shall continue in full force and effect unless and until terminated in accordance with Section 8. The parties understand and agree that termination of the rights and obligations of the parties under Sections 2 and 7.1.2 [Co-Branded Equipment Listings] in accordance with this Section 7.1.3 [Review of Payments] shall not permit either party to terminate this Agreement pursuant to Section 8.2 [Termination for Cause]. 7.1.4. Professional e-Bookstore Sales. VerticalNet will pay PaperExchange ***** of the
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Extract the exact clause related to "Parties" from the excerpt above.