1. A’Hearn M.F. and Feldman, P.D. 1980, Ap. J. Lett., 242, L 187.
2. Aikman, G.C.L., Balfour, W.J. and Tatum, J.B. 1974, Icarus, 21, 303.
3. Arpigny, C. 1964, Ann. d’Ap., 27, 406.
4. Arpigny, C. 1966, Ap. J. 144, 424.
5. Arpigny, C. 1974, The Study of Comets, Eds. B. Donn, M. Mumma, W. Jackson, M. A’Hearn and R. Harrington, NASA SP-393, p. 797.