@article{MAN_1981__256_163512,
     author = {Kung-Fu Ng and Michel Duhoux},
     title = {Directedness in {Ordered} {Normed} {Spaces} and {Operators.}},
     journal = {Mathematische Annalen},
     pages = {281--288},
     publisher = {mathdoc},
     volume = {256},
     year = {1981},
     zbl = {0493.46022},
     url = {http://geodesic.mathdoc.fr/item/MAN_1981__256_163512/}
}