@article{MASLO_1980_30_4_a7,
     author = {Dvure\v{c}enskij, Anatolij and Pulmannov\'a, Sylvia},
     title = {On the sum of observables in a logic},
     journal = {Mathematica slovaca},
     pages = {393--399},
     year = {1980},
     volume = {30},
     number = {4},
     mrnumber = {595300},
     zbl = {0454.03030},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/MASLO_1980_30_4_a7/}
}