@article{TMF_1976_28_3_a13,
     author = {V. K. Tkachenko},
     title = {Magnon-magnon interaction in a~square lattice},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {424--429},
     year = {1976},
     volume = {28},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1976_28_3_a13/}
}