@article{ZNSL_2003_301_a4,
     author = {L. Yu. Kolotilina},
     title = {Bounds for the extreme eigenvalues of block~$2\times2$ {Hermitian} matrices},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {172--194},
     publisher = {mathdoc},
     volume = {301},
     year = {2003},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2003_301_a4/}
}