Photographic observations of Pluto 1991-1994 with the Baldone Schmidt telescopeV. P. Ryl'kov, A. A. Dement'eva, A. Alksnis and J. I. StraumeAstron. Astrophys. Suppl. Ser., 118 1 (1996) 105-110DOI: https://doi.org/10.1051/aas:1996184