Abstract: | Institute of theoretical Astrophysics, Oslo, Norway; Department of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences; Department of Astronomy and McDonald Observatory, Austin, Texas, USA; Department of Physics and Astronomy, University of Arkansas at Little Rock, Arkansas, USA; Byurakan Astrophysical Observatory Armenian Academy of Sciences, USSR. Published in English in Astrofizika, Vol. 19, No. 1, 67–73, July–August, 1988. |