@article{SM_1972_18_1_a1,
     author = {V. A. Kondrat'ev and T. G. Pletneva and S. D. \`Eidel'man},
     title = {Positive solutions of linear quasielliptic evolution equations},
     journal = {Sbornik. Mathematics},
     pages = {15--44},
     publisher = {mathdoc},
     volume = {18},
     number = {1},
     year = {1972},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1972_18_1_a1/}
}