@article{TMF_1969_1_1_a2,
     author = {I. V. Polubarinov},
     title = {Variational principle and nonconserved operators},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {34--49},
     publisher = {mathdoc},
     volume = {1},
     number = {1},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1969_1_1_a2/}
}