@article{10_1017_S0017089511000346,
     author = {AIENA, PIETRO and GONZ\'ALEZ, MANUEL and MART\'INEZ-ABEJ\'ON, ANTONIO},
     title = {CHARACTERIZATIONS {OF} {STRICTLY} {SINGULAR} {AND} {STRICTLY} {COSINGULAR} {OPERATORS} {BY} {PERTURBATION} {CLASSES}},
     journal = {Glasgow mathematical journal},
     pages = {87--96},
     year = {2012},
     volume = {54},
     number = {1},
     doi = {10.1017/S0017089511000346},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089511000346/}
}