@article{MAN_1990__288_1_164734,
     author = {Zolt\'an Sasv\'ari and Heinz Langer},
     title = {Definitizing polynomials of unitary and {Hermitian} operators in {Pontrjagin} spaces.},
     journal = {Mathematische Annalen},
     pages = {231--244},
     publisher = {mathdoc},
     volume = {288},
     number = {1},
     year = {1990},
     zbl = {0694.47018},
     url = {http://geodesic.mathdoc.fr/item/MAN_1990__288_1_164734/}
}