Treaties, States Parties and Commentaries
Treaties and Documents
Geneva Conventions of 1949 and Additional Protocols, and their Commentaries
Historical Treaties and Documents
Rules concerning the Control of Wireless Telegraphy in Time of War and Air Warfare. Drafted by a Commission of Jurists at the Hague, December 1922 - February 1923.
Part II: Rules of Air Warfare#Chapter III: Belligerents. - Art. 15.
Art. 15. The crews of military aircraft shall bear a fixed distinctive emblem of such a nature as to be recognizable at a distance in the event of crews finding themselves separated from the aircraft.