Commutative symmetric operator families of the so-called -class are considered in Krein spaces. It is proved that the restriction of a family of this type on a special kind of invariant subspace is similar to a family of operators adjoint to multiplication operators by scalar functions acting on a suitable function space.
"Models of Function Type for Commutative Symmetric Operator Families in Krein Spaces." Abstr. Appl. Anal. 2008 1 - 40, 2008. https://doi.org/10.1155/2008/439781