@article{STO_1982__6_1_38861,
     author = {Salvatore Guccione and Roberto Tortora},
     title = {A semantical hierarchy for modal formulas.},
     journal = {Stochastica},
     pages = {71},
     publisher = {mathdoc},
     volume = {6},
     number = {1},
     year = {1982},
     mrnumber = {MR0694205},
     zbl = {0513.03011},
     language = {en},
     url = {https://geodesic-test.mathdoc.fr/item/STO_1982__6_1_38861/}
}