échange de lettres

Source : DFAE, [Guide de la pratique en matière de traités internationaux](https://www.eda.admin.ch/dam/eda/fr/documents/publications/Voelkerrecht/Praxisleitfaden-Voelkerrechtliche-Vertraege_fr.pdf), édition 2015, p. 5 (1.4.2016).

Source : EDA, [ABC der Diplomatie](https://www.eda.admin.ch/content/dam/eda/de/documents/publications/GlossarezurAussenpolitik/ABC-Diplomatie_de.pdf), Diplomatische Note, S. 10 (1.4.2016).

Source : DFAE, [ABC della diplomazia](https://www.eda.admin.ch/content/dam/eda/it/documents/publications/GlossarezurAussenpolitik/ABC-Diplomatie_it.pdf), 2008, pag. 36 (12.4.2016).

Treaties are commonly constituted by an exchange of instruments, known as 'exchange of notes', 'exchange of diplomatic notes' or 'exchange of letters' which often provide that the agreement constituted by the exchange of notes/or letters will not enter into force until each has informed the other that its constitutional formalities have been completed. The terminological difference between 'exchange of notes' and 'exchange of letters' is not legally significant.

Source : FDFA, [Practice Guide to International Treaties](https://www.eda.admin.ch/dam/eda/en/documents/publications/Voelkerrecht/Praxisleitfaden-Voelkerrechtliche-Vertraege_en.pdf), Edition 2015, p. 5 (1.4.2016).