"Werra". CJ's Classic Camera Collection. Retrieved 18 May 2023.
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DE Patent 56109C, Paul Rudolph, "Photographisches Doppelobjectiv", published May 20, 1891, assigned to Carl Zeiss AG
GB Patent 189322607A, H. Dennis Taylor, "A Simplified Form and Improved Type of Photographic Lens", published October 6, 1894, assigned to Taylor, Taylor & Hobson
GB Patent 189516640A, Hugh Lancelot Aldis, "Improvements in Photographic Lenses", published July 4, 1896, assigned to J.H. Dallmeyer, Ltd.
DE Patent 134408C, Paul Rudolph, "Sphärisch und chromatisch korrigirtes Objektiv mit anastigmatischer Bildebenung", published October 10, 1902, assigned to Carl Zeiss Jena
DE Patent 142294C, Paul Rudolph, "Sphärisch, chromatisch und astigmatisch korrigiertes Objectiv aus vier, durch die Blende in zwei Gruppen geteilten Linsen", published July 4, 1903, assigned to Carl Zeiss Jena
DE Patent 603325C, Ernst Wandersleb & Willy Merté, "Dreiteiliges photographisches Objektiv", published September 29, 1934, assigned to Carl Zeiss Jena
DE Patent 451194C, Wandersleb & Merté, "Sphaerisch, komatisch, chromatisch und astigmatisch korrigierte Lichtbildlinse", published October 22, 1927
GB Patent 191329637A, John Stuart & John W. Hasselkus, "Improvements in Lenses for use in Photography and Projection, or the like.", published October 22, 1914
US Patent 1122895A, Charles Henri Florian, "Objective", published December 29, 1914, assigned to Berthiot
DE Patent 343086C, "Unsymmetrisches Objektiv", published October 28, 1921, assigned to E. Leitz
US Patent 2084714A, Albrecht Tronnier, "Unsymmetrical photographic objective", published June 22, 1937, assigned to Jos. Schenider & Co.
US Patent 2573511A, Albrecht Tronnier, "Four-lens photographic objective", published October 30, 1951, assigned to Voigtländer & Sohn AG
US Patent 721240A, Paul Rudolph, "Photographic Objective", published February 24, 1903, assigned to Carl Zeiss Jena
