https://digital.katalog.queersearch.org/s/katalog/item/44801, “"Mein liebes Tierchen ... In inniger Liebe Dein Alfred": Briefe und Karten an seine Tochter Hannah Busoni”, https://digital.katalog.queersearch.org/s/katalog/item/50680, QueerSearch, accessed 4. Mai 2025, https://digital.katalog.queersearch.org/s/katalog/item/28963