@article{UFA_2017_9_1_a1,
     author = {I. N. Braeutigam and K. A. Mirzoev and T. A. Safonova},
     title = {On deficiency index for some second order vector differential operators},
     journal = {Ufa mathematical journal},
     pages = {18--28},
     publisher = {mathdoc},
     volume = {9},
     number = {1},
     year = {2017},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/UFA_2017_9_1_a1/}
}