Retrieved 22 December 2019. ↑ Asimov 1972, p. 123. ↑ Bishop 1958, p. 7. ↑ Thomson 1958, p. 12. sfn error: no target: CITEREFThomson1958 (help) ↑ Bishop 1958, p. 17. 1 2 3 Spitzer 1958. ↑ Furth 1981, p. 275. sfn error: no target: CITEREFFurth1981 (help) ↑ Spitzer 1958, p. 181. ↑ Spitzer 1958, pp. 182–183. ↑ Spitzer 1958, p. 183. 1 2 3 Spitzer 1958, p. 188. ↑ Spitzer, L. (1960).