@article{DE_1973_9_11_a13,
     author = {\`E. M. Saak},
     title = {The solvability of the {Dirichlet} problem for an elliptic equation of order $21$ in the class $W_2^{(2l)}$},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2048--2051},
     publisher = {mathdoc},
     volume = {9},
     number = {11},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_11_a13/}
}