Art. 15 CISG
(1) An offer becomes effective when it reaches the offeree.
(2) An offer, even if it is irrevocable, may be withdrawn if the withdrawal reaches the offeree before or at the same time as the offer.
The Secretariat Commentary on Art. 13 of the 1978 New York Draft, predecessor to Art. 15 CISG, gives insight into the drafters' unterstanding on the eve of the 1980 Vienna Diplomatic Conference.
Overview of case law on Art. 15 CISG: UNCITRAL Digest
The UNCITRAL Digest on the CISG can be used as a starting point to discover the relevant case law on this article.