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:
"""
ordered Products in the Territory. Payment to be made upon shipment. Source: PRECHECK HEALTH SERVICES, INC., 8-K, 3/20/2020 12. In the event of termination, neither party, their heirs nor successors shall issue any challenge whatsoever to contest the termination. 13. The Distributor is an independent contractor and nothing contained in this agreement shall be deemed or interpreted to constitute the Distributor as a partner or employee of the Principal, nor shall either party have any authority to bind the other in any respect, it being understood and agreed that all orders submitted by the Distributor are subject to acceptance by Principal in its sole discretion. 14. It is agreed between the parties that there are no other agreements or understandings between them relating to the subject matter of this Agreement. This Agreement supersedes all prior agreements, oral or written, between the parties and is intended as a complete and exclusive statement of the agreement between the parties. No change or modification of this Agreement shall be valid unless the same be in writing and signed by the parties. 15. This Agreement shall not be assigned by the Distributor without the prior written consent of the Principal. 16. Official communication from Distributor or the Principal shall be in written form or by email, acknowledged by the recipient. 17. This Agreement shall be construed in accordance with and governed by the laws of the State of Texas without regard to principles of conflicts of laws. 18. Each of Principal and Distributor represents that it has the right to enter into this Agreement and that this Agreement does not violate any agreement to which it is a party. Principal represents that it owns or has rights to the intellectual property embodied in the Products. Intending to be legally bound, the parties hereto have caused this Agreement to be executed as of the date first above written. BY /s/ Cameron Gundry BY /s/ Justin Anderson Cameron Gundry, Dir. of Commercialization Justin Anderson, CEO Co-Diagnostics, Inc. PreCheck Health Services, Inc. (Principal) (Distributor) Source: PRECHECK HEALTH SERVICES, INC., 8-K, 3/20/2020 .EXHIBIT A LIST OF PRODUCTS Source: PRECHECK HEALTH SERVICES, INC., 8-K, 3/20/2020 Source: PRECHECK HEALTH SERVICES, INC., 8-K, 3/20/2020 Source: PRECHECK HEALTH SERVICES, INC., 8-K, 3/20/2020
"""

Extract the exact clause related to "Anti-Assignment" from the excerpt above.

assistant: This Agreement shall not be assigned by the Distributor without the prior written consent of the Principal.