@article{MZ_1989__201_4_174065,
     author = {Palle E.T. Jorgensen},
     title = {Positive {Definite} {Functions} on the {Heisenberg} {Group.}},
     journal = {Mathematische Zeitschrift},
     pages = {455--476},
     publisher = {mathdoc},
     volume = {201},
     number = {4},
     year = {1989},
     zbl = {0702.43004},
     url = {http://geodesic.mathdoc.fr/item/MZ_1989__201_4_174065/}
}