Esche, P. G. (1975). Carl Zeiss Jena. Carl Zeiss Jena.
Cita Chicago (17th ed.)Esche, Paul Gerhard. Carl Zeiss Jena. Jena: Carl Zeiss Jena, 1975.
Cita MLA (8th ed.)Esche, Paul Gerhard. Carl Zeiss Jena. Carl Zeiss Jena, 1975.
Atenció: Aquestes cites poden no estar 100% correctes.