@article{MZ_1982__180_173180,
     author = {Paul Ressel and Jens P.R. Christensen},
     title = {Positive {Definite} {Kernels} on the {Complex} {Hilbert} {Sphere.}},
     journal = {Mathematische Zeitschrift},
     pages = {193--202},
     publisher = {mathdoc},
     volume = {180},
     year = {1982},
     zbl = {0572.43004},
     url = {http://geodesic.mathdoc.fr/item/MZ_1982__180_173180/}
}