@article{10_4064_sm158_3_1,
     author = {Heydar Radjavi and Ping-Kwan Tam and Kok-Keong Tan},
     title = {A perturbation characterization of compactness
 of self-adjoint operators},
     journal = {Studia Mathematica},
     pages = {199--205},
     publisher = {mathdoc},
     volume = {158},
     number = {3},
     year = {2003},
     doi = {10.4064/sm158-3-1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/sm158-3-1/}
}