Art. 12 CISG
Any provision of article 11, article 29 or Part II of this Convention that allows a contract of sale or its modification or termination by agreement or any offer, acceptance or other indication of intention to be made in any form other than in writing does not apply where any party has his place of business in a Contracting State which has made a declaration under article 96 of this Convention. The parties may not derogate from or vary the effect of this article.
The Secretariat Commentary on Art. 11 of the 1978 New York Draft, predecessor to Art. 12 CISG, gives insight into the drafters' unterstanding on the eve of the 1980 Vienna Diplomatic Conference.
CISG-AC Opinion regarding Art. 12 CISG
CISG-AC Opinion No. 15 ‘Reservations under Articles 95 and 96 CISG’ (Rapporteur: Ulrich G. Schroeter), adopted by the CISG Advisory Council following its 18th meeting in Beijing (China) on 21 and 22 October 2013
Overview of case law on Art. 12 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.