@article{LKN_2008_a0,
     author = {A. G. Sergeev},
     title = {Harmonic maps},
     journal = {Lekcionnye kursy NOC},
     pages = {3--117},
     publisher = {mathdoc},
     year = {2008},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/LKN_2008_a0/}
}