Other forms of international agreements are the following:

(a) A protocol, which is either in the form of official minutes, giving conclusions of an international conference, and signed at the end of each session by the negotiators, or a preliminary draft of an agreement to be afterwards reduced into the form of a treaty.

(b) Cartels, which are agreements between belligerents regulating intercourse during war

(c) Declarations.

(d) Memoranda, and

(e) Letters.

8 Wilson and Tucker on International Law, Sec. 85