@article{DAN_1977_232_1_a5,
     author = {Yu. P. Krivenkov},
     title = {Necessary optimality conditions for a linear problem with second order differential equations of elliptic type in the presence of phase constraints},
     journal = {Doklady Akademii Nauk},
     pages = {28--31},
     publisher = {mathdoc},
     volume = {232},
     number = {1},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1977_232_1_a5/}
}