by Sopka, R. J., Hildebrand, R., Jaffe, D. T., Gatley, I., Roellig, T.
Published in The Astrophysical journal (01.07.1985)

by Sopka, R. J., Herbig, G., Michalitsianos, A. G., Kafatos, M.
Published in The Astrophysical journal (01.07.1982)

by SOPKA, ROBERT J.
Published in Publications of the Astronomical Society of the Pacific (01.01.1988)