@article{SF_1986__33_134801,
     author = {G.M.S. Gomes},
     title = {The lattice of {R-unipotent} congruences on a regular semigroup.},
     journal = {Semigroup forum},
     pages = {159--174},
     publisher = {mathdoc},
     volume = {33},
     year = {1986},
     zbl = {0582.20049},
     url = {http://geodesic.mathdoc.fr/item/SF_1986__33_134801/}
}