@article{EXMATH_1999_1999_1_a4,
     author = {Berm\'udez, Teresa and Gonz\'alez, Manuel},
     title = {Los operadores casi regulares son regulares.},
     journal = {Extracta mathematicae},
     pages = {41-43},
     year = {1999},
     volume = {14},
     number = {1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EXMATH_1999_1999_1_a4/}
}