@article{FPM_1998_4_1_a1,
     author = {S. A. Bogatyi},
     title = {Ljusternik--Schnirelman theorem and $\beta f$},
     journal = {Fundamentalʹna\^a i prikladna\^a matematika},
     pages = {11--38},
     publisher = {mathdoc},
     volume = {4},
     number = {1},
     year = {1998},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FPM_1998_4_1_a1/}
}