@article{IM2_1971_5_5_a10,
     author = {V. I. Liberzon and V. S. Shul'man},
     title = {Operator-irreducible symmetric algebras of operators in the $\mathbf\Pi^1$ {Pontryagin} space},
     journal = {Izvestiya. Mathematics},
     pages = {1168--1179},
     year = {1971},
     volume = {5},
     number = {5},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1971_5_5_a10/}
}