Cook, A. (1969). Gravity and the earth. Wykeham.
Cita Chicago (17th ed.)Cook, A.H. Gravity and the Earth. London: Wykeham, 1969.
Cita MLA (9th ed.)Cook, A.H. Gravity and the Earth. Wykeham, 1969.
Atenció: Aquestes cites poden no estar 100% correctes.