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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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 instrument. {***} 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 10 of 28 H. Prior to their release, the parties must agree on press releases or market communication that utilises the other Party's name. Counterparts; Integration; Effectiveness; Electronic Execution This Agreement may be executed in counterparts (and by different parties hereto in different counterparts), each of which shall constitute an original, but all of which when taken together shall constitute a single contract. This Agreement constitutes the entire contract among the parties relating to the subject matter hereof and supersede any and all previous agreements and understandings, oral or written, relating to the subject matter hereof. This Agreement shall become effective when it shall have been executed by all parties and upon receipt of all counterparts hereof that, when taken together, bear the signatures of each of the other parties hereto. Delivery of an executed counterpart of a signature page of this Agreement by e- mail and/or telecopy shall be effective as delivery of a manually executed counterpart of this Agreement. The words "execution," "signed," "signature," and words of like shall be deemed to include electronic signatures or the keeping of records in electronic form, each of which shall be of the same legal effect, validity or enforceability as a manually executed signature or the use of a paper- based recordkeeping system, as the case may be, to the extent and as provided for in any applicable law, including the Federal Electronic Signatures in Global and National Commerce Act, and any other similar State laws based on the Uniform Electronic Transactions Act. IN WITNESS WHEREOF, the parties have executed this Agreement as of the last date below and in so doing acknowledge that they have a corporate authority to bind their respective organizations to this Agreement. SCIENTIFIC PRODUCTS PHARMACEUTICAL CO. LTD: HEMISPHERX BIOPHARMA, INC: S/ Saleh Al-Abdullah Al-Rasheed S/ Thomas K. Equels Saleh Al-Abdullah Al-Rasheed Thomas K. Equels CEO & Owner President and CEO Date: Date: 3-29-2016 3-31-16 {***} 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 11 of 28 Exhibit 1 The drug, Interferon Alfa-n3, is intended for investigational use in the countries in which it is distributed prior to receipt of RAA; The drug, Interferon Alfa-n3, meets your specifications as reflected on the attached Certificate of Analysis; The drug, Interferon Alfa-n3, is not in conflict with the laws of the countries in which it is distributed; The investigation will be conducted in accordance with good clinical practices, including review and approval of the study by an independent ethics panel and informed consent of the study subjects; The drug, Interferon Alfa-n3, does not present an imminent hazard to public health, either in the United States, if the drug were to be reimported, or in the countries in which it is distributed; The drug, Interferon Alfa-n3, is labelled in accordance with the laws of the countries in which it is distributed. I have reviewed the attached labels and the current Certificate of Analysis against the specifications and agree with the above statements that these meet the laws of the countries in which the product will be distributed. Signature: __________________________________ Date: ______________________ Printed Name: Saleh Al- Rashid Title: Chairman and CEO Company: Scientific Products Pharmaceutical Co. LTD {***} Confidential portions of this exhibit have been redacted and
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Extract the exact clause related to "Covenant Not To Sue" from the excerpt above.