@article{TRSPY_2006_255_a8,
     author = {P. L. Gurevich},
     title = {On the {Stability} of the {Index} of {Unbounded} {Nonlocal} {Operators} in {Sobolev} {Spaces}},
     journal = {Informatics and Automation},
     pages = {116--135},
     publisher = {mathdoc},
     volume = {255},
     year = {2006},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TRSPY_2006_255_a8/}
}