@article{PORMA_1985__43_1_114494,
     author = {Queir\'o, Jo\~ao Filipe},
     title = {Generalized approximation numbers},
     journal = {Portugaliae mathematica},
     pages = {157--166},
     publisher = {mathdoc},
     volume = {43},
     number = {1},
     year = {1985},
     mrnumber = {0875064},
     zbl = {0601.15007},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1985__43_1_114494/}
}