Artikel 20 hbv:
The present Convention shall not prevent an agreement between any two or more Contracting States to dispense with ยน
a) the necessity for duplicate copies of transmitted documents as required by the second paragraph of Article 3,
b) the language requirements of the third paragraph of Article 5 and Article 7,
c) the provisions of the fourth paragraph of Article 5,
d) the provisions of the second paragraph of Article 12.