@article{EXMATH_1989_1989_1_a28,
     author = {Alvarez, Jos\'e A. and Alvarez, Teresa and Gonz\'alez, Manuel},
     title = {Brechas y perturbaciones de operadores no de {semi-Fredholm.}},
     journal = {Extracta mathematicae},
     pages = {139-141},
     publisher = {mathdoc},
     volume = {4},
     number = {3},
     year = {1989},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EXMATH_1989_1989_1_a28/}
}