Art. 11 CISG
A contract of sale need not be concluded in or evidenced by writing and is not subject to any other requirement as to form. It may be proved by any means, including witnesses.
The Secretariat Commentary on Art. 10 of the 1978 New York Draft, predecessor to Art. 11 CISG, gives insight into the drafters' unterstanding on the eve of the 1980 Vienna Diplomatic Conference.
CISG-AC Opinion regarding Art. 11 CISG
CISG-AC Opinion No. 3 ‘Parol Evidence Rule, Plain Meaning Rule, Contractual Merger Clause and the CISG’ (Rapporteur: Richard Hyland), adopted by the CISG Advisory Council at its 7th meeting in Madrid (Spain) on 23 October 2004
CISG-AC Opinion No. 17 ‘Limitation and Exclusion Clauses in CISG Contracts’ (Rapporteur: Lauro Gama, Jr.), adopted by the CISG Advisory Council following its 21st meeting in Bogotá (Colombia) on 16 October 2015
Overview of case law on Art. 11 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.