@article{10_1017_S001708950000327X,
     author = {Crabb, M. J. and Spain, P. G.},
     title = {Commutators and normal operators},
     journal = {Glasgow mathematical journal},
     pages = {197--198},
     year = {1977},
     volume = {18},
     number = {2},
     doi = {10.1017/S001708950000327X},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S001708950000327X/}
}