1. American Ephemeris and Nautical Almanac--1979: 231 (1977).
2. Born, M., Principles of Optics: CH13 (1959).
3. HUEBNER, W.F., DIMINUTION OF COMETARY HEADS DUE TO PERIHELION PASSAGE, ZEITSCHRIFT FUR ASTROPHYSIK 65: 185 (1967).
4. KOOMEN, M.J., WHITE-LIGHT CORONAGRAPH IN OSO-7, APPLIED OPTICS 14: 743 (1975).
5. ASTRONOMISCHE ABHANDLUNGEN 1901 1 1 Untersuchungen uber das System der Cometen 1843 I 1880 I und 1882 II. 3.