@article{MZM_1969_6_1_a7,
     author = {M. M. Gekhtman},
     title = {Self-adjoint abstract differential operators},
     journal = {Matemati\v{c}eskie zametki},
     pages = {65--72},
     publisher = {mathdoc},
     volume = {6},
     number = {1},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1969_6_1_a7/}
}