@article{IM2_1975_9_6_a5,
     author = {V. G. Limanskii},
     title = {On differential-operator equations of second order},
     journal = {Izvestiya. Mathematics},
     pages = {1241--1277},
     year = {1975},
     volume = {9},
     number = {6},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1975_9_6_a5/}
}