Cita APA (7th ed.)

Markham, C. R. (1876). The threshold of the unknown region. Fourth edition with supplementary chapters (4a. ed.). Sampson Low, Marston, Searle & Rivington.

Cita Chicago (17th ed.)

Markham, Clements Robert. The Threshold of the Unknown Region. Fourth Edition with Supplementary Chapters. 4a. ed. Londres: Sampson Low, Marston, Searle & Rivington, 1876.

Cita MLA (9th ed.)

Markham, Clements Robert. The Threshold of the Unknown Region. Fourth Edition with Supplementary Chapters. 4a. ed. Sampson Low, Marston, Searle & Rivington, 1876.