@article{ZNSL_1971_22_a5,
     author = {A. S. Markus and L. N. Nikol'skaya and N. K. Nikol'skii},
     title = {On the unitary spectrum of contraction operators in the {Banach} space},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {65--74},
     publisher = {mathdoc},
     volume = {22},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1971_22_a5/}
}