@article{PORMA_1994__51_4_47311,
     author = {Umar, Abdullahi},
     title = {A class of quasi-adequate transformation semigroups.},
     journal = {Portugaliae mathematica},
     pages = {553--570},
     publisher = {mathdoc},
     volume = {51},
     number = {4},
     year = {1994},
     zbl = {0828.20066},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1994__51_4_47311/}
}