https://digital.katalog.queersearch.org/s/katalog/item/45096 and https://digital.katalog.queersearch.org/s/katalog/item/47498, “Der Urning: Selbstbewusst schwul vor 1900”, https://digital.katalog.queersearch.org/s/katalog/item/48887, QueerSearch, accessed 2. Mai 2025, https://digital.katalog.queersearch.org/s/katalog/item/35355