@article{ZNSL_1989_178_a4,
     author = {M. Sh. Birman and M. Z. Solomyak},
     title = {Estimates for the difference of the fractional powers of self-adjoint operators under unbounded perturbations},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {120--145},
     publisher = {mathdoc},
     volume = {178},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1989_178_a4/}
}