@article{DAN_1973_208_6_a1,
     author = {V. I. Gorbachuk and M. L. Gorbachuk},
     title = {On boundary-value problems for a first-order differential equation with operator coefficients and the expansion in eigenfunctions of this equation},
     journal = {Doklady Akademii Nauk},
     pages = {1268--1271},
     publisher = {mathdoc},
     volume = {208},
     number = {6},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1973_208_6_a1/}
}