%0 Journal Article %A V. I. Mossakovskii %A A. A. Novopashin %A A. G. Biskup %T Certain aspects of the Riemann problem for the case of an equation with four singular points %J Differencialʹnye uravneniâ %D 1975 %P 445-455 %V 11 %N 3 %I mathdoc %U http://geodesic.mathdoc.fr/item/DE_1975_11_3_a3/ %G ru %F DE_1975_11_3_a3