| 27 November 1919 |
|
Treaty of Peace between the Allied and Associated Powers and Bulgaria, and Protocol. |
| 20 November 1975 |
|
Protocol introducing amendments to the Arrangements between Certain Member States of the European Space Research Organisation and the European Space Research Organisation concerning the Execution of an Aeronautical Satellite Programme |
| 17 December 1975 |
29 April 1977 |
Protocol concerning the Exploitation of a Pre-Operational Meteorological Satellite (Meteosat) |