@article{10_21136_AM_1984_104106,
     author = {Dittrich, Jaroslav},
     title = {On the topological charge conservation in the three-dimensional ${\rm O}(3)$ $\sigma$-model.},
     journal = {Applications of Mathematics},
     pages = {367--371},
     publisher = {mathdoc},
     volume = {29},
     number = {5},
     year = {1984},
     doi = {10.21136/AM.1984.104106},
     mrnumber = {0772271},
     zbl = {0568.58019},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/AM.1984.104106/}
}