@article{10_4153_CJM_1981_067_9,
     author = {Akemann, Charles A. and Walter, Martin E.},
     title = {Unbounded {Negative} {Definite} {Functions}},
     journal = {Canadian journal of mathematics},
     pages = {862--871},
     year = {1981},
     volume = {33},
     number = {4},
     doi = {10.4153/CJM-1981-067-9},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1981-067-9/}
}