@article{10_4064_cm_41_1_1_12,
     author = {R. Beazer and D. S. Macnab},
     title = {Modal extensions of {Heyting} algebras},
     journal = {Colloquium Mathematicum},
     pages = {1--12},
     publisher = {mathdoc},
     volume = {41},
     number = {1},
     year = {1979},
     doi = {10.4064/cm-41-1-1-12},
     language = {fr},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-41-1-1-12/}
}