Geodesic
Regular factorization of the scalar characteristic function
Zapiski Nauchnykh Seminarov POMI, Investigations on linear operators and function theory. Part 28, Tome 270 (2000), pp. 19-50 
M. F. Gamal'. Regular factorization of the scalar characteristic function. Zapiski Nauchnykh Seminarov POMI, Investigations on linear operators and function theory. Part 28, Tome 270 (2000), pp. 19-50. http://geodesic.mathdoc.fr/item/ZNSL_2000_270_a1/
@article{ZNSL_2000_270_a1,
     author = {M. F. Gamal'},
     title = {Regular factorization of the scalar characteristic function},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {19--50},
     year = {2000},
     volume = {270},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2000_270_a1/}
}
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Voir la notice du chapitre de livre provenant de la source Math-Net.Ru

It is known that the regular factorizations of the characteristic function of an operator describe its invariant subspaces. The case of a scalar characteristic function is considered. Some examples are given. Factorizations describing all chains of invariant subspaces that contain a given subspace $L$ are constructed in terms of the factorization describing $L$. A representation of the regular factorization of a function is obtained in terms of factorizations of its inner and outer parts.