@article{TMF_1991_86_3_a7,
     author = {M. K. Volkov and A. A. Osipov},
     title = {$\pi a_1${~Transitions} and low-energy limit in the linear sigma model},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {385--390},
     publisher = {mathdoc},
     volume = {86},
     number = {3},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1991_86_3_a7/}
}