@article{ZNSL_2011_389_a6,
     author = {I. V. Kurbatova},
     title = {Functional calculus generated by a~square pencil},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {113--130},
     publisher = {mathdoc},
     volume = {389},
     year = {2011},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2011_389_a6/}
}