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:
"""
[Confidential Treatment Requested] Exhibit 10.11 CO-BRANDING AGREEMENT This Co-Branding Agreement (this "Agreement") dated March 3, 2000 (the "Effective Date") is entered into between VerticalNet, Inc., a Pennsylvania corporation having a principal place of business at 700 Dresher Road, Suite 100, Horsham, Pennsylvania, 19044 ("VerticalNet"), and Impresse Corporation, a California Corporation, having a principal place of business at 1309 South Mary Avenue, Sunnyvale, California, 94087 ("Impresse"). BACKGROUND WHEREAS, VerticalNet owns and operates a series of Online Communities (defined below) that are accessible via the World Wide Web, each of which is designed to be an online gathering place for businesses of a certain type or within a certain industry; and WHEREAS, Impresse desires to provide its commercial printing services (the "Impresse Services") to Users (defined below) of VerticalNet Sites (defined below); and WHEREAS, Impresse and VerticalNet desire to create Co-Branded Site (defined below) where users will be able to register to review and utilize the Impresse Services and to promote such Co-Branded Site on VerticalNet Sites. NOW, THEREFORE, in consideration of the mutual covenants herein, and intending to be legally bound hereby, VerticalNet and Impresse agree as follows: 1. DEFINITIONS 1.1. AFFILIATE shall mean, when used with reference to a party, any individual or entity directly or indirectly controlling, controlled by or under common control with such party. For purposes of this definition, "control" means the direct or indirect ownership of at least 50% of the outstanding voting securities of a party, or the right to control the policy decisions of such party. 1.2. BANNER shall mean a graphical image advertising the Impresse Site that is posted in an area reasonably designated by VerticalNet for similar banner advertisements and shall contain a Link (defined below) to the Co-Branded Site. 1.3. CO-BRANDED CONTENT shall mean all materials, data and similar information presented on the pages of the Co-Branded Site. 1.4. CO-BRANDED SITE shall mean the Site (defined below) that contains both a Frame (defined below) and a Window (defined below) which includes the Impresse Area (defined below) and the VerticalNet Area (defined below) of the Co-Branded Site. 1.5. CONFIDENTIAL INFORMATION shall mean, subject to the provisions of Section 7.2 [EXCLUSIONS], all proprietary and confidential information of a party, including, without limitation, trade secrets, technical information, business information, sales information, customer and potential customer lists and identities, product sales plans, sublicense agreements, inventions, developments, discoveries, software, know-how, methods, techniques, formulae, data, processes and other trade secrets and proprietary ideas, whether or not protectable under patent, trademark, copyright or other areas of law, that the other party has access to or receives. For purposes of this Agreement, 1 * Represents confidential information for which Impresse Corporation is seeking confidential treatment with the Securities and Exchange Commission. the Co-Branded Content shall not be considered Confidential Information of Impresse. For purposes of this Agreement, this Agreement shall be considered Confidential Information. 1.6. E-COMMERCE CENTER shall mean a web page on a VerticalNet Site which is customized by VerticalNet to include a vendor's information, including the vendor's branding; a Link to the vendor's catalog, auction item listings; the vendor's career center including employment information; archives of; and Links to other related content locations. 1.7. FRAME shall mean a portion of a Web page which surrounds a Window on the top and left. 1.8. IMPRESSE AREA shall mean the Window portion of the Impresse Site (defined below) less the Frame that will be placed around the Window of the Co-Branded Site. 1.9. IMPRESSE MARK shall mean any trademark, service mark, trade name, domain name, design or logo of Impresse or its Affiliates. 1.10. IMPRESSE SITE shall mean the Site located at www.impresse.com (and any successor Site thereto). 1.11. IMPRESSE-VERTICALNET REVENUE shall have the meaning defined in Section 4.6.2 [REVENUE SHARING]. 1.12. INTELLECTUAL PROPERTY shall mean any and all trade secrets, patents, copyrights, trademarks, service marks, URLs, trade dress, brand features, know-how and similar rights of any type under the laws of any applicable governmental authority, including, without limitation, all applications and registrations relating to any of the foregoing. 1.13. INTELLECTUAL PROPERTY RIGHTS shall mean all rights in and to Intellectual Property, including, without limitation, all patent rights, copyrights, trademarks, service marks, know-how and trade secrets. 1.14. LAUNCH DATE shall mean the day on which the Co-Branded Site and the V-Solutions Area become fully operational and generally available on the Internet. 1.15. LINK shall mean a link, including but not limited to a hyperlink, Source: IMPRESSE CORP, S-1/A, 3/22/2000 button or banner, that connects two Sites in a manner
"""

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

assistant: Not found.