@article{MAT_1957_1_3_a4,
     author = {L. G\r{a}rding},
     title = {Eigenfunction expansions connected with elliptic differential operators},
     journal = {Matematika},
     pages = {107--116},
     publisher = {mathdoc},
     volume = {1},
     number = {3},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MAT_1957_1_3_a4/}
}