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:
"""
Person other than SIGA or MMT or an Affiliate of either of them. "Tier 1 Countries" mean [***]. "Tier 2 Countries" mean [***]. "Tier 3 Countries" mean [***]. "Tier Period" has the meaning set forth in Section 4.2. "Trademark" means any trademark, service mark, trade name, brand name, sub-brand name, trade dress, product configuration, program name, product name, delivery form name, certification mark, collective mark, logo, tagline, slogan, design or business symbol, that functions as an identifier of source or origin, whether or not registered and all statutory and common law rights therein and all registrations and applications therefor, together with all goodwill associated with, or symbolized by, any of the foregoing. "U.S." means the United States of America, including all of its territories and possessions. "VAT" has the meaning set forth in Section 6.8(c). "Yearly Collected Revenue" means Net Product Sales Amount that is collected during the applicable Calendar Year. 10 Source: SIGA TECHNOLOGIES INC, 8-K, 6/3/2019 ARTICLE 2 GRANT OF RIGHTS 2.1 Grant of Rights to MMT. (a) Grant to MMT. Subject to the terms and conditions of this Agreement, SIGA hereby grants to MMT an exclusive right and license, with the right to grant sublicenses as permitted under Section 2.1(b), under the SIGA Intellectual Property solely to Promote the Product in the Field in the Territory. The license granted by SIGA to MMT under this Section 2.1(a) will be exclusive even as to SIGA with respect to rights to Promote the Product in the Field in the Territory, except as set forth in Section 2.4 below. (b) Sublicense Rights. Except for the subcontractors appointed by MMT as of the Effective Date as listed on Exhibit A attached hereto, MMT may not grant sublicenses of the rights and licenses granted to it in Section 2.1(a) to any Affiliate (including Pfizer or any Affiliate of Pfizer) or Third Party without the prior written approval of SIGA (such approval not to be unreasonably withheld). Each such subcontractor listed on Exhibit A attached hereto and any Affiliate or Third Party approved by SIGA as an MMT sublicensee pursuant to this Section 2.1(b) shall be deemed to be a "Permitted Sublicensee" for purposes of this Agreement. (c) Potential New Field. From time to time, MMT may request to expand the Field in a particular country in the Territory because it believes that there is an opportunity to Promote the Product in such new field (a "Potential New Field"). MMT shall make such request to SIGA in writing. SIGA will determine whether to approve such Potential New Field, based upon available information regarding the regulatory environment in such country for such Potential New Field, and whether SIGA will need to seek Regulatory Approval and Pricing Approval and Reimbursement Approval. The Parties shall discuss the Potential New Field in good faith and upon the mutual written agreement of the Parties to proceed with a Potential New Field in such country, such Potential New Field shall be deemed hereunder to be an "Expanded Field" for purposes of that country only in the Territory. 2.2 Negative Covenants. (a) MMT will not, and will not permit any of its Affiliates or sublicensees to, use or practice any SIGA Intellectual Property outside the scope of the licenses granted to it under Section 2.1. (b) SIGA will not, and will not permit any of its Affiliates or licensees to, Promote the Product in the Field in the Territory, except as set forth in Section 2.4. 2.3 Non-Compete Covenant. During the Term, MMT shall not Commercialize in any manner any Competing Product in the Field in any country in the Territory; provided, however, the Parties hereby acknowledge that the restrictions set forth in this Section 2.3 shall not apply to any Affiliates of MMT (including Pfizer). Furthermore, [***]. 11 Source: SIGA TECHNOLOGIES INC, 8-K, 6/3/2019 2.4 Retained Rights. Notwithstanding anything herein to the contrary, SIGA retains the right on behalf of itself and its Affiliates, licensees or any Third Parties to Develop, Manufacture, supply, distribute and otherwise Commercialize the Product in Field the Territory, except that SIGA may not Promote or Sell or Offer to Sell the Product in the Field in the Territory to any Third Party; provided that SIGA may, at its sole cost and discretion engage in promotional activities regarding (but not enter into any Customer Contracts in respect of) the Product in support of MMT's efforts to Promote or Sell and Offer to Sell the Product. 2.5 No Implied Licenses. Except as explicitly set forth in
"""

Extract the exact clause related to "Irrevocable Or Perpetual License" from the excerpt above.