@article{SF_1986__33_134802,
     author = {G.M.S. Gomes},
     title = {Some results on congruences on {R-unipotent} semigroups.},
     journal = {Semigroup forum},
     pages = {175--186},
     publisher = {mathdoc},
     volume = {33},
     year = {1986},
     zbl = {0582.20050},
     url = {http://geodesic.mathdoc.fr/item/SF_1986__33_134802/}
}