Markham, C. R. (1876). The threshold of the unknown region. Fourth edition with supplementary chapters (4a. ed.). Sampson Low, Marston, Searle & Rivington.
Citazione stile Chigago Style (17a edizione)Markham, Clements Robert. The Threshold of the Unknown Region. Fourth Edition with Supplementary Chapters. 4a. ed. Londres: Sampson Low, Marston, Searle & Rivington, 1876.
Citatione MLA (9a ed.)Markham, Clements Robert. The Threshold of the Unknown Region. Fourth Edition with Supplementary Chapters. 4a. ed. Sampson Low, Marston, Searle & Rivington, 1876.
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