@article{MZ_1987__195_183709,
     author = {G. Groenewegen and A. van Rooij},
     title = {The {Modulus} of a {Weakly} {Compact} {Operator.}},
     journal = {Mathematische Zeitschrift},
     pages = {473--480},
     publisher = {mathdoc},
     volume = {195},
     year = {1987},
     zbl = {0611.47032},
     url = {http://geodesic.mathdoc.fr/item/MZ_1987__195_183709/}
}