1. Publications of the Astronomical Institute of the Academy of Sciences of the Czech Republic Creator: Guth, V. and Sehnal, L. Type: model:periodicalitem and TEXT Language: Czech and English Description: 47 and The visual observations of artificial satellites 1957α1,α2, 1957β and 1958δ1,δ2 Rights: http://creativecommons.org/publicdomain/mark/1.0/ and policy:public