@article{BAG_1991__31_138470,
     author = {D. Lau and B. Schr\"oder},
     title = {On the number of closed subsets of linear functions in the 6-valued logic},
     journal = {Beitr\"age zur Algebra und Geometrie},
     pages = {19--32},
     publisher = {mathdoc},
     volume = {31},
     year = {1991},
     url = {http://geodesic.mathdoc.fr/item/BAG_1991__31_138470/}
}