@article{SM_1973_21_3_a7,
     author = {V. A. Tkachenko},
     title = {On~the uniqueness of an expansion in generalized eigenfunctions of a~differential operator},
     journal = {Sbornik. Mathematics},
     pages = {455--466},
     year = {1973},
     volume = {21},
     number = {3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1973_21_3_a7/}
}