@article{DAN_1987_296_3_a2,
     author = {E. P. Eroshenkov and T. Sh. Kal'menov},
     title = {Completeness of the root vectors of the elliptic {Bitsadze--Samarskii} problem},
     journal = {Doklady Akademii Nauk},
     pages = {528--531},
     publisher = {mathdoc},
     volume = {296},
     number = {3},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1987_296_3_a2/}
}