@article{CMUC_1973__14_2_a7,
     author = {Varlet, Jules C.},
     title = {Nodal filters in semilattices},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {263--277},
     publisher = {mathdoc},
     volume = {14},
     number = {2},
     year = {1973},
     mrnumber = {0327597},
     zbl = {0276.06002},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1973__14_2_a7/}
}