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:
"""
EXHIBIT 10.53 SPONSORSHIP AGREEMENT for Boxing Event in China, on April 22, 2000 American Champion Media, Inc. ("ACM"), a Delaware company with headquarters at 1694 The Alameda, San Jose, CA 95126, U.S.A., is the host and producer of a boxing event to take place at the Tian He Stadium in Guangzhou, China (the "Event"). This Event is scheduled to take place on April 22, 2000, and this Sponsorship Agreement (the "Agreement") dated as of April 14, 2000 is made by and between Shun Li De Commerce & Trading Ltd ("SLD") a Beijing company, with headquarters at Xin Xing Dong Xiang, Bldg 1 Suite 1413, Xi Cheng District, Beijing, China (the "Sponsor") and ACM. 1) The Sponsor wishes to become a sponsor of the Event, a production of ACM, to take place on April 22, 2000 at the Tian He Stadium in Guangzhou, China. 2) As a sponsor of the Event, the Sponsor is entitled to the following sponsorship components: * Two Floor Cards (12in x 66in) in prominent position for TV camera * Two Drapes over ropes (5in x 60in, with lettering within the middle 36") * Two Ring Side banners (200cm x 15cm) * One overhead banner (5ft x 8 ft) to be hung over boxing ring * Other handout materials for audience 3) For the above sponsorship components, the Sponsor agrees to pay ACM a total amount of US$400,000.00. The amount is payable 180 days from the date of the Event. 4) This is understood between the parties that SLD may resale all or some of the above sponsorship components to other buyers, provided that SLD shall submit third party display materials at least five days prior to the event for ACM's approval. 5) ACM retains all of its rights under copyright and trademark laws pertaining to the Event's intellectual property, whether registered or unregistered, and any applications of the Event's logo, name, characters and likeness. Video and audio excerpts of the Event must have ACM's approval in writing prior to such use. The Sponsor shall retain all of its rights under copyright and trademark laws pertaining to any of its intellectual property. 6) Display materials from the Sponsor must be delivered to the Tian He Stadium at least two days prior to the event. 7) All covenants, promises and agreements by or on behalf of the parties contained in this Agreement shall be binding upon and shall inure to the benefit of the successors and assigns of the parties; but nothing in this Agreement, expressed or implied is intended to confer on any party the right to assign its rights or obligations hereunder. Nothing in this Agreement, whether expressed or implied, is intended to confer any rights or remedies under or by reason of this Agreement on any persons other than the parties to it and their respective successors and assigns, nor is anything in this Agreement intended to relieve or discharge the obligation or liability of any third persons to any party to this Agreement, nor shall any provision give any third person any right of subrogation or action over or against any party to this Agreement. 8) This Agreement shall be governed by, and construed and enforced in accordance with, the laws of the State of California and the laws of Hong Kong. In the event of a dispute, the parties shall seek mediation at a third country mutually agreed upon. 9) This Agreement sets forth the entire agreement of the parties hereto with regard to the subject matter hereof and supersedes and replaces all prior agreements, understandings and representations, oral or written, with regard to such matter. 10) This Agreement may be executed in two or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same instrument. IN WITNESS WHEREOF, the parties have caused this Agreement to be duly executed as of the date hereby written. /s/ Anthony K. Chan Anthony K. Chan Chief Executive Officer American Champion Media, Inc. /s/ He, Li He, Li Chief Financial Officer Shun Li De Commerce & Trading Ltd
"""

Extract the exact clause related to "Warranty Duration" from the excerpt above.

assistant: Not found.