@article{SF_1972__4_133895,
     author = {K.H. Hofmann and J.M. Day},
     title = {Clan acts and codimension.},
     journal = {Semigroup forum},
     pages = {206--214},
     publisher = {mathdoc},
     volume = {4},
     year = {1972},
     zbl = {0255.54032},
     url = {http://geodesic.mathdoc.fr/item/SF_1972__4_133895/}
}