@article{TMF_1973_16_2_a3,
     author = {L. N. Labzovskii},
     title = {Variational principle for the elements of the $S$ matrix},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {178--185},
     publisher = {mathdoc},
     volume = {16},
     number = {2},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1973_16_2_a3/}
}