Cita APA (7th ed.)
Nicholson, S. B. (1938). Magnetic Observations of sunspots 1917-24.
Cita Chicago (17th ed.)
Nicholson, Seth Barnes. Magnetic Observations of Sunspots 1917-24. 1938.
Cita MLA (9th ed.)
Nicholson, Seth Barnes. Magnetic Observations of Sunspots 1917-24. 1938.
Atenció: Aquestes cites poden no estar 100% correctes.