@article{10_4153_CJM_1988_066_x,
     author = {Herrero, Domingo A.},
     title = {On the {Essential} {Spectra} of {Quasisimilar} {Operators}},
     journal = {Canadian journal of mathematics},
     pages = {1436--1457},
     year = {1988},
     volume = {40},
     number = {6},
     doi = {10.4153/CJM-1988-066-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1988-066-x/}
}