@article{MASLO_2006__56_5_a7,
     author = {Gudder, Stan},
     title = {An order for quantum observables},
     journal = {Mathematica slovaca},
     pages = {573--589},
     publisher = {mathdoc},
     volume = {56},
     number = {5},
     year = {2006},
     mrnumber = {2293588},
     zbl = {1141.81008},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/MASLO_2006__56_5_a7/}
}