VARIATIONAL-PRINCIPLES FOR HYPOELLIPTIC EQUATIONS ArticleFILIPPOV V.M.Doklady Akademii nauk SSSR. Vol. 285. 1985. P.. 302-305
SPECTRAL PROPERTIES OF OPERATORS IN THE PROBLEM OF THE COMPRESSIBLE FLUID OSCILLATION IN ROTATING VESSELS ArticlePAL P.K.Doklady Akademii nauk SSSR. Vol. 281. 1985. P.. 529-534