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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withheld or delayed. 16. TERMS AND TERMINATION 16.1 Term. Unless earlier terminated, this Agreement shall continue in effect until the expiration of the Royalty Term as defined in Section 1.87 ("Term"), and thereafter Green Cross has no remaining payment obligations with respect to the Products pursuant to Section 8.5 above and MacroGenics shall have no further obligations hereunder. 16.2 Termination for Change in Control of Green Cross. In the event of a Change in Control involving Green Cross, Green Cross shall provide prompt written notice to MacroGenics following such Change in Control, and MacroGenics may, in its sole discretion, terminate this Agreement by providing written notice to Green Cross within *** of MacroGenics' receipt of such written notice of the Change in Control. 16.3 Termination for Change in Control of MacroGenics. In the event of a Change in Control involving MacroGenics, MacroGenics shall provide prompt written notice to Green Cross following such Change in Control, and Green Cross may, in its sole discretion, terminate this Agreement by providing written notice to MacroGenics within *** of Green Cross' receipt of such written notice of the Change in Control. 16.4 Termination for Challenge to Patent Validity. MacroGenics may terminate this Agreement immediately upon written notice to Green Cross in the event Green Cross or any of its Affiliates: (a) directly or indirectly oppose, or assist any Third Party to oppose, in any patent office proceeding, the grant of any patent or patent application within the MacroGenics Licensed Patents, or, in any patent office proceeding, dispute or directly or indirectly assist any Third Party to dispute, the validity of any patent within the MacroGenics Licensed Patents or any of the claims thereof, including opposing any application for amendment thereto; *** = Portions of this exhibit have been omitted pursuant to a request for confidential treatment. An unredacted version of this exhibit has been filed separately with the Commission. 46 (b) directly or indirectly oppose, or assist any Third Party to oppose, in any court proceeding, the grant of any patent or patent application within the MacroGenics Licensed Patents, or, in any court proceeding, dispute or directly or indirectly assist any Third Party to dispute, the validity of any patent within the MacroGenics Licensed Patents or any of the claims thereof; or (c) bring any claim or proceedings of whatever nature in relation to the MacroGenics Licensed Patents against MacroGenics and/or any of MacroGenics' Affiliates (or in respect of the foregoing their directors and officers) in respect of any activities carried out by them under any MacroGenics Licensed Patents which may be the subject of a Valid Claim of the MacroGenics Licensed Patents. 16.5 Termination for Cause. This Agreement may be terminated at any time during the Term upon written notice by either Party if the other Party is in material breach of its other obligations under this Agreement and, in each case, has not cured such breach within *** after notice requesting cure of the breach (other than for non-payment which shall be cured within ***). 16.6 Effect of Termination (a) If MacroGenics terminates this Agreement pursuant to Section 16.2, 16.4, or pursuant to Section 16.5 for cause based on material breach by Green Cross: (i) Green Cross shall pay any amounts due pursuant to Section 8 prior to the date of termination; (ii) For the avoidance of doubt, the licenses and sublicenses granted to Green Cross under Sections 10.1(a) and 10.4 shall terminate; (iii) Green Cross shall return to MacroGenics all Products (including, without limitation, all MGAH22) within its possession or control and arrange for the Green Cross Sublicensees to return to MacroGenics all Products (including, without limitation, all MGAH22) within such Green Cross Sublicensees' possession or control; (iv) Green Cross shall cease to research, develop, market and sell any Product that infringes a Valid Claim in a MacroGenics Licensed Patent; (v) for the Products (including, without limitation, MGAH22), Green Cross shall assign and promptly transfer to MacroGenics, at no expense to MacroGenics, all of Green Cross' right, title and interest in and to (A) all regulatory filings (such as INDs, CTAs and drug master files), Regulatory Approvals, and clinical trial agreements (to the extent assignable and not cancelled) for such Products(s), to the extent that MacroGenics elects to continue development of such Product(s); (B) all data, including clinical data, materials and information of any kind *** = Portions of this exhibit have been omitted pursuant to a request for confidential treatment. An unredacted version of this exhibit has been filed separately
"""

Extract the exact clause related to "Covenant Not To Sue" from the excerpt above.

assistant: MacroGenics may terminate this Agreement immediately upon written notice to Green Cross in the event Green Cross or any of its Affiliates: (a) directly or indirectly oppose, or assist any Third Party to oppose, in any patent office proceeding, the grant of any patent or patent application within the MacroGenics Licensed Patents, or, in any patent office proceeding, dispute or directly or indirectly assist any Third Party to dispute, the validity of any patent within the MacroGenics Licensed Patents or any of the claims thereof, including opposing any application for amendment thereto;