– Cantus Planus Regensburg: https//www.cantusplanus.de/index.html
– CLORI – Archivio della cantata italiana: https://cantataitaliana.it/
– Gallica (Bibliothèque Nationale de France): https://gallica.bnf.fr/accueil/it/content/accueil-it?mode=desktop
– Internet Archive: https://archive.org/
– The LiederNet Archive: https://www.lieder.net/lieder/
– RIdIM (Répertoire International d’Iconographie Musicale): https://ridim.org/
– RISM (Répertoire International des Sources Musicales): https://rism.info/