@article{SF_1990__40_1_135020,
     author = {K.D. jr. Magill and P.R. Misra},
     title = {Principal continuum congruences, regular ...-classes and local subsemigroups.},
     journal = {Semigroup forum},
     pages = {205--226},
     publisher = {mathdoc},
     volume = {40},
     number = {1},
     year = {1990},
     zbl = {0692.20055},
     url = {http://geodesic.mathdoc.fr/item/SF_1990__40_1_135020/}
}