Dietze, O. (1973). Riddles and puzzles. Volk und Wissen.
Cita Chicago (17th ed.)Dietze, Otto. Riddles and Puzzles. Berlin: Volk und Wissen, 1973.
Cita MLA (8th ed.)Dietze, Otto. Riddles and Puzzles. Volk und Wissen, 1973.
Atenció: Aquestes cites poden no estar 100% correctes.