Bhat, C. L; Rannot, R. C; Mohapatra, D. K; Gandhi, V. N; Tickoo, A. K; Kaul, R; Kaul, S. K; Kaul, S. R; Goyal, H. C; Bhatt, N(Astronomical Society of India, 1999)
Nikolsky, S. I; Sinitsyna, V. G; Acobian, A. M; Matizov, B; Vorobiov, S. P; Bhat, C. L; Tickoo, A. K; Rannot, R. C; Sapru, M. L; Razdan, H(Astronomical Society of India, 1993)