Oppenheim, E. P. (1923). The seven conundrums. Little, Brown, and Co..
Lua i Stíl Chicago (17ú heag.)Oppenheim, E. Phillips. The Seven Conundrums. Boston: Little, Brown, and Co., 1923.
Lua MLA (8ú heag.)Oppenheim, E. Phillips. The Seven Conundrums. Little, Brown, and Co., 1923.
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