@article{CMFD_2006_15_a6,
     author = {V. I. Burenkov and P. D. Lamberti and M. Lanza de Cristoforis},
     title = {Spectral {Stability} of {Nonnegative} {Self-Adjoint} {Operators}},
     journal = {Contemporary Mathematics. Fundamental Directions},
     pages = {76--111},
     publisher = {mathdoc},
     volume = {15},
     year = {2006},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/CMFD_2006_15_a6/}
}