Art. 16 CISG
(1) Until a contract is concluded an offer may be revoked if the revocation reaches the offeree before he has dispatched an acceptance.
(2) However, an offer cannot be revoked:
(a) if it indicates, whether by stating a fixed time for acceptance or otherwise, that it is irrevocable; or
(b) if it was reasonable for the offeree to rely on the offer as being irrevocable and the offeree has acted in reliance on the offer.
The Secretariat Commentary on Art. 14 of the 1978 New York Draft, predecessor to Art. 16 CISG, gives insight into the drafters' unterstanding on the eve of the 1980 Vienna Diplomatic Conference.
Overview of case law on Art. 16 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.