【正文】 o such specific system is deemed its time of arrival。 if no specific system has been designated, the time when the electronic message first enters into any of the recipient39。s systems is deemed its time of arrival.Article 17 Withdrawal of OfferAn offer may be withdrawn. The notice of withdrawal shall reach the offeree before or at the same time as the offer.Article 18 Revocation of OfferAn offer may be revoked. The notice of revocation shall reach the offeree before it has dispatched a notice of acceptance.Article 19 Irrevocable OfferAn offer may not be revoked:(i) if it expressly indicates, whether by stating a fixed time for acceptance or otherwise, that it is irrevocable。(ii) if the offeree has reason to regard the offer as irrevocable, and has undertaken preparation for performance.Article 20 Extinguishment of OfferAn offer is extinguished in any of the following circumstances:(i) The notice of rejection reaches the offeror。(ii) The offeror lawfully revokes the offer。(iii) The offeree fails to dispatch its acceptance at the end of the period for acceptance。(iv) The offeree makes a material change to the terms of the offer.Article 21 Definition of AcceptanceAn acceptance is the offeree39。s manifestation of intention to assent to an offer.Article 22 Mode of Acceptance。 Acceptance by ConductAn acceptance shall be manifested by notification, except where it may be manifested by conduct in accordance with the relevant usage or as indicated in the offer.Article 23 Timely Dispatch of AcceptanceAn acceptance shall reach the offeror within the period prescribed in the offer.Where the offer does not prescribe a period for acceptance, the acceptance shall reach the offeror as follows:(i) Where the offer is made orally, the acceptance shall be dispatched immediately, unless otherwise agreed by the parties。(ii) Where the offer is made in a nonoral manner, the acceptance shall reach the offeror within a reasonable time.Article 24 Commencement of the Period for AcceptanceWhere an offer is made by a letter or a telegram, the period for acceptance mences on the date shown on the letter or the date on which the telegram is handed in for dispatch. If the letter does not specify a date, the period mences on the posting date stamped on the envelop. Where the offer is made through an instantaneous munication device such as telephone or facsimile, etc., the period for acceptance mences once the offer reaches the offeree.Article 25 Contract Formed upon Effectiveness of AcceptanceA contract is formed once the acceptance bees effective.Article 26 Effectiveness of AcceptanceA notice of acceptance bees effective once it reaches the offeror. Where the acceptance does not require notification, it bees effective once an act of acceptance is performed in accordance with the relevant usage or as required by the offer.Where a contract is concluded by the exchange of electronic messages, the time of arrival of the acceptance shall be governed by Paragraph 2 of Article 16 hereof.Article 27 Withdrawal of AcceptanceAn acceptance may be withdrawn. The notice of withdrawal shall reach the offeror before or at the same time as the acceptance.Article 28 Late AcceptanceAn acceptance dispatched by the offeree after expiration of the period for acceptance constitutes a new offer, unless the offeror timely advises the offeree that the acceptance is valid.Article 29 Delayed Transmission of AcceptanceIf the offeree dispatched its acceptance within the period for acceptance, and the acceptance, which would otherwise have reached the offeror in due time under normal circumstances, reaches the offeror after expiration of the period for acceptance due to any other reason, the acceptance is valid, unless the offeror timely advises the offeree that the acceptance has been rejected on grounds of the delay.Article 30 Acceptance Containing Material ChangeThe terms of the acceptance shall be identical to those of the offer. A purported acceptance dispatched by the offeree which materially alters the terms of the offer constitutes a new offer. A change in the subject matter, quantity, quality, price or remuneration, time, place and method of performance, liabilities for breach of contract or method of dispute resolution is a material change to the terms of the offer.Article 31 Acceptance Containing Nonmaterial Changes An acceptance containing nonmaterial changes to the terms of the offer is nevertheless valid and the terms thereof prevail as the terms of the contract, unless the offeror timely objects to such changes or the offer indicated that acceptance may not contain any change to the terms thereof.Article 32 Time of Formation in Case of Memorandum of ContractWhere the parties enter into a contract by a memorandum of contract, the contract is formed when it is signed or sealed by the parties. Article 33 Time of Formation in Case of Letters or Electronic Messages。 Confirmation LetterWhere the parties enter into a contract by the exchange of letters or electronic messages, one party may require execution of a confirmation letter before the contract is formed. The contract is formed upon execution of the confirmation letter. Article 34 Place of Formation。 Electronic MessagesThe place where the acceptance bees effective is the place of formation of a contract.Where a contract is concluded by the exchange of electronic messages, the recipient39。s main place of business is the place of formation of the contract。 if the recipient does not have a main place of business, its habitual residence is the place of formation of the contract. If the parties have agreed otherwise, such agreement prevails.Article 35 Place of Formation in Case of Memorandum of ContractWhere a contract is concluded by a memorandum of contract, its place of formation is the place where the parties sign or seal the contract.Article 36 Effect of Failure to Conclude Contract in Writing