a . “What Happened to the Earth’s Helium?” New Scientist, Vol. 24, 3 December 1964, pp. 631–632.
u Melvin A. Cook, Prehistory and Earth Models (London: Max Parrish, 1966), pp. 10 –14.
u Melvin A. Cook, “Where is the Earth’s Radiogenic Helium?” Nature, Vol. 179, 26 January 1957, p. 213.
u Joseph W. Chamberlain, Theory of Planetary Atmospheres (New York: Academic Press, 1987), pp. 371–372.