Coba jelasin Jurnal dari Peter Carl Ludwig Schwarz dong

EMWS , 23 November 1894.

Kropotkin (1903), (Prince) Pyotr Alexeyevich; and Freshfield, Douglas W., "Obituary. Dr. Gustav Radde." The Geographical Journal, Vol. 21, No. 5 (May, 1903), pp. 563–565. The Royal Geographical Society (publisher).

MNRAS (1888), Monthly Notices of the Royal Astronomical Society, Volume 48 (1887-1888), Burlington House, London; Spottiswoode & Co., London (publisher); entry as: Dorpat, Kaiserliche Universitats-Sternwarte, Band xvii. Angestellt und herausgegeben von Ludwig Schwarz.

. November 1894 issue. United Kingdom.

Outlook, , 10 November 1894 issue, necrology entry for October 3.

PASP, , San Francisco, USA.