Article 8 Montreal Convention
Article 8 of the Montreal Convention (Convention For the Unification of Certain Rules for International Carriage by Air) is titled Documentation for Multiple Packages. It is under Chapter II (Documentation and Duties of the Parties Relating to the Carriage of Passengers, Baggage and Cargo).
When there is more than one package:
(a) the carrier of cargo has the right to require the consignor to make out separate air waybills;
(b) the consignor has the right to require the carrier to deliver separate cargo receipts when the other means referred to in paragraph 2 of Article 4 are used.
See also: Article 7 Montreal Convention