https://digital.katalog.queersearch.org/s/katalog/item/43181, “In Memory of Karl Heinrich Ulrichs: Author of the Latin Jouranl Alaudae: Supplemented by The Restoration by Magnus Hirschfeld, Vindex, the Vindictar by Karl Heinrich Ulrichs, Critical Arrows by Karl Heinrich Ulrichs”, https://digital.katalog.queersearch.org/s/katalog/item/49217, QueerSearch, accessed 29. April 2025, https://digital.katalog.queersearch.org/s/katalog/item/25656