@article{DE_1996_32_5_a12,
     author = {I. L. Makarov},
     title = {Exact and truncated variational schemes in the case of a selfadjoint spectral problem for a fourth-order equation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {670--675},
     publisher = {mathdoc},
     volume = {32},
     number = {5},
     year = {1996},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1996_32_5_a12/}
}