@article{IM2_1968_2_6_a6,
     author = {A. M. Perelomov and V. S. Popov},
     title = {Casimir operators for semisimple {Lie} groups},
     journal = {Izvestiya. Mathematics },
     pages = {1313--1335},
     publisher = {mathdoc},
     volume = {2},
     number = {6},
     year = {1968},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1968_2_6_a6/}
}