%0 Journal Article %A O. E. Orel %T Rotation function for integrable problems reducing to the Abel equations. Orbital classification of Goryachev–Chaplygin systems. %J Sbornik. Mathematics %D 1995 %P 271-296 %V 186 %N 2 %U http://geodesic.mathdoc.fr/item/SM_1995_186_2_a6/ %G en %F SM_1995_186_2_a6