Klaus, G. (1968). Was ist - was soll. Urania-Verlag.
Citação do estilo Chicago (17ª ed.)Klaus, Georg. Was Ist - Was Soll. Leipzig: Urania-Verlag, 1968.
Citação MLA (8ª ed.)Klaus, Georg. Was Ist - Was Soll. Urania-Verlag, 1968.
Nota: a formatação da citação pode não corresponder 100% ao definido pela respectiva norma.