[300] A. Fowler, Proc. Roy. Soc., 73A, 219, 1904; M. N. R. A. S., 69, 508, 1909.

[301] Hale, Adams and Gale, Ap. J., 24, 185, 1906; Hale and Adams, ibid., 25, 75, 1907.

[302] Rep. of Spectral Class. Comm., I. A. U., 1925.

[303] W. F. Meggers, J. Wash. Ac. Sci., 13, 317, 1923; ibid., 14, 151, 1924.

[304] Menzel, H. C. 258, 1924.

[305] Ap. J., 25, 235, 1907.

[306] J. Op. Soc. Am., 9, 355, 1924.

[307] Catalan, An. Soc. Espan. Fis. y Quim., 21, 84, 1923.

[308] Russell, Mt. W. Contr., in press.

[309] Chapter VIII, [p. 124].