@article{IM_1988__94_2_143634,
     author = {Bernd Carl and Alain Pajor},
     title = {Gelfand numbers of operators with values in a {Hilbert} space.},
     journal = {Inventiones mathematicae},
     pages = {479--504},
     publisher = {mathdoc},
     volume = {94},
     number = {2},
     year = {1988},
     zbl = {0668.47014},
     url = {http://geodesic.mathdoc.fr/item/IM_1988__94_2_143634/}
}