"The Nebulosity, Herschel V 34 (GC 1193) NGC 1990" from Atti della Pontificia Accademia delle Scienze Nuovi Lincei, Anno LXXX, Sessione II, 16 Gennaio,, 1927

"The Nebulosity, Herschel V 34 (GC 1193) NGC 1990" from Atti della Pontificia Accademia delle Scienze Nuovi Lincei, Anno LXXX, Sessione II, 16 Gennaio,, 1927, box-folder: 40. Georgetown Observatory Collection, GRB-000010. Georgetown University Rare Books , Booth Family Center for Special Collections. https://findingaids.library.georgetown.edu/repositories/14/archival_objects/1163471 Accessed May 12, 2024.