@article{TM_1992_201_a10,
     author = {V. A. Il'in and E. I. Moiseev},
     title = {On the systems consisting of subsets of root function of two distinct boundary value problems},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {219--230},
     publisher = {mathdoc},
     volume = {201},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TM_1992_201_a10/}
}