1. Art. XVIII.—Notes on Hindu Astronomy and the History of our Knowledge of it
2. 2. G. R. Kaye "Hindu Astronomy", MASI, No. 18, Calcutta, 1924 , pp.7 -9 .
3. 4. O. Neugebauer ESA, p. 160 ; pp.160 -73 . Also his "Babylonian Planetary Theory", Proc. APS, 98 (1), February 1954, p. 65 21, p. 77 note 47.
4. Tamil Astronomy: A Study in the History of Astronomy in India