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:
"""
to the sums that are not objected by the SENDER, pursuant to the term established in this clause. ECOPETROL shall issue the note credit or equivalent document respect to the sums objected by the SENDER, in order to rectify the inaccuracy. 3 CLAUSE EIGHTH BONDS 8.1 The SENDER may pay in advance the Service for the Contracted Capacity, in which case the corresponding invoice shall be adjusted pursuant to the provisions in the Clause of Terms of Payment as it may apply. 8.2 Otherwise, In order to guarantee compliance with all and each of the obligations of the SENDER under the Contract hereof, including but without being limited to the payment of the Fee, the SENDER is obliged to constitute in favor of ECOPETROL and to deliver within ten (10) business days after the subscription of the Contract hereof for the amount indicated in the Specific Conditions (hereinafter, the "Bond"): a) A performance policy for the payment of Services issued by an insurance policy legally established in the country, governed by the General Clauses of ECOPETROL indicated in Annex 3; or b) An irrevocable stand-by letter of credit at first requirement, issued by (i) a banking establishment authorized to operate in Colombia with AAA credit rating for its long-term debt in pesos, o (ii) a foreign financial entity with representation or a confirming and payment bank in Colombia, with risk credit of long term debt in dollars no less than the rating for the foreign sovereign debt of Colombia issued pursuant to the International Standby Practices (ISP98) of the International Chamber of Commerce, for which, it may be used the form contained in Annex 4 of the Contract hereof. 8.3 The Bond shall be valid during all the term of execution of the Contract plus one hundred twenty (120) calendar days. 7.7 ECOPETROL, in order to facilitate and expedite the verification of the invoices by the SENDER shall deliver via e-mail the same day of its preparation and in PDF format, to the account of institutional e-mail registered by the SENDER, a copy of the invoices and corresponding debit and credit vouchers. 7.8 The SENDER shall pay late interests on any unpaid amounts pursuant to the provisions set out by ECOPETROL in the Guidelines for Administration of Service Receivables ECP-UTE-G-008 or a document that modifies or supersedes it, which is an integral part of the Contract hereto as Annex 2. 7.9 The shipment tax shall be invoiced in Colombian pesos upon obtaining the corresponding liquidation from the Ministry of Mines and Energy and shall be paid to ECOPETROL by the SENDER, within the fifteen (15) calendar days after ECOPETROL files in the offices of the SENDER the corresponding bills or invoices. 7.10 The amounts deposited by the SENDER in any of the bank accounts of ECOPETROL must come from the accounts owned by the SENDER, who by means of written communication before the subscription of the Contract will certify the origin of funds. This in accordance with the Policy for the Prevention and Control of Asset Laundering of ECOPETROL. 4 8.4 In the case of local financial institutions, the bond shall expressly state that the issuer waves the benefit of excussio stipulated in article 2383 of the Colombian Civil Code. 8.5 The issuance and validity of the Bond shall be an indispensable condition for the provision of the Service. As a consequence, ECOPETROL may suspend the provision of the Service or terminate the Contract in advance, when the Bond is not in force, without this waiving the SENDER from its payment obligations and all other obligations derived from the Contract hereof. CLAUSE NINTH OBLIGATIONS OF THE SHIPPER 9.1 In addition to the obligations set forth in the Manual of the Shipper and those established in the law, ECOPETROL is obliged in a special manner to: CLAUSE TENTH OBLIGATIONS OF THE SENDER 10.1 In addition to the obligations set out in the Manual of the Shipper and those in the law, the SENDER is obliged particularly to: a) Receive in the Entrance Point agreed in the Pipeline, the Crude owned by the SENDER up to the volume corresponding to the Contracted Capacity, subject to the Available Capacity of the Pipeline in the Month of Operation in which the Service is to be provided. b) Maintain in custody the Crude delivered from the Point of Entrance until the time of delivery to the SENDER in the Exit Point. Notwithstanding the foregoing, in the event in which the SENDER does not receive the
"""

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