@article{SF_1977__14_186366,
     author = {R.W. Yoh},
     title = {Congruence relations on left canonic semigroups.},
     journal = {Semigroup forum},
     pages = {175--184},
     publisher = {mathdoc},
     volume = {14},
     year = {1977},
     zbl = {0396.20043},
     url = {http://geodesic.mathdoc.fr/item/SF_1977__14_186366/}
}