@article{DAN_1969_187_4_a20,
     author = {M. E. Perel'man},
     title = {Alternative properties of physical systems and spectral representations in the field theory},
     journal = {Doklady Akademii Nauk},
     pages = {781--783},
     publisher = {mathdoc},
     volume = {187},
     number = {4},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1969_187_4_a20/}
}