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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HEMISPHERX for the purpose of securing and preserving HEMISPHERX's rights. K. It is agreed that nothing contained in this Sales, Marketing, Distribution, and Supply Agreement shall be construed as an assignment or grant to the SCIEN of any rights, title or interest in or to "Interferon alfa-n3 (human leukocyte derived)". L. It is further understood that all rights relating thereto are reserved by HEMISPHERX, except for the license hereunder to SCIEN of the right to use and utilize the name Interferon alfa-n3 (human leukocyte derived) only as specifically and expressly provided in this Agreement. M. In the event of termination of this license for any reason, SCIEN shall within 6months (as described in the Termination clause), cease all use of the "Interferon alfa-n3 (human leukocyte derived)". SCIEN shall not thereafter use any names, mark or trade name similar thereto belonging to HEMISPHERX. Termination of the license under the provisions of this Agreement shall be without prejudice to any rights which HEMISPHERX may otherwise have against SCIEN. N. SCIEN shall, and shall cause its shareholders, officers, directors, and managing personnel to, comply with all laws, rules and government regulations pertaining to its business and shall not violate any laws which would create an adverse effect on "Interferon alfa-n3 (human leukocyte derived)" in the U.S. and/or the Territory. O. Relationship of Parties. SCIEN shall not in any manner or respect be the legal representative or agent of HEMISPHERX and shall not enter into or create any contracts, Agreements, or obligations on the part of HEMISPHERX, either expressed or implied, nor bind HEMISPHERX in any manner or respect whatsoever regarding its intellectual property; it being understood that this Agreement is only a contract for the licensed use of the product names in connection with the terms in this Agreement. {***} Confidential portions of this exhibit have been redacted and filed separately with the Commission pursuant to a confidential treatment request in accordance with Rule 24b-2 of the Securities Exchange Act of 1934, as amended. Page 9 of 28 XIII. BUYOUT HEMISPHERX will have the option at any time to buy out this Agreement. If exercised within the first two (2) years HEMISPHERX will pay SCIEN three (3) times the Product sales for the preceding 12 months. If exercised after year 3, HEMISPHERX will pay SCIEN two (2) times the Product sales for the preceding 12 months. XIV. MISCELLANEOUS. A. Notices. Notices sent pursuant to this Agreement are valid if in writing and addressed to the parties at the respective addresses given below or at such other addresses as either party shall notify the other in writing and sent by registered or certified mail, postage prepaid and return receipt requested, or by Federal Express or other comparable courier providing proof of delivery, and shall be deemed duly given and received (i) if mailed, on the third business day following the mailing thereof, or (ii) if sent by courier, the date of its receipt (or if not on a business day, the next succeeding business day). If to HEMISPHERX: Thomas K. Equels, President and CEO One Penn Center 1617 JFK Boulevard Suite 500 Philadelphia, PA 19103 United States If to SCIEN: Abdelrhman Mofeed Zhreldin Business Development Manager Scientific Products Pharmaceutical Co. Ltd Tahlia Street, P.O Box 10485, Riyadh 11433 Saudi Arabia B. This Agreement and the transactions contemplated herein shall be governed by, and construed in accordance with, the laws of the State of Delaware, USA and disputes, if not resolved by the Parties, will be settled by binding arbitration in and under the rules of arbitration in London, England. C. This Agreement constitutes the entire understanding of the parties with respect to the purchase and sale of Products and supersedes all prior discussions, agreements, and understandings between HEMISPHERX and SCIEN. D. Each party an independent contractor to the other and the relationship between the parties shall not be construed to be that of an employer and employee, or to constitute a partnership, joint venture, or agency of any kind. E. This Agreement may only be amended in a writing signed by both parties hereto. F. If any provision of this Agreement is declared invalid or unenforceable by a court having competent jurisdiction, it is mutually agreed that this Agreement shall endure except for the part declared invalid or unenforceable by order of such court. G. This Agreement may be executed in one or more counterparts, each of which shall be deemed an original, but all of which together shall constitute one and the same
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Extract the exact clause related to "Expiration Date" from the excerpt above.