@article{10_4153_CJM_1968_125_0,
     author = {Gudder, Stanley P.},
     title = {Complete {Sets} of {Observables} and {Pure} {States}},
     journal = {Canadian journal of mathematics},
     pages = {1276--1280},
     year = {1968},
     volume = {20},
     number = {1},
     doi = {10.4153/CJM-1968-125-0},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1968-125-0/}
}