@article{PORMA_1994__51_2_47075,
     author = {Garba, G.U.},
     title = {On the idempotent ranks of certain semigroups of order-preserving transformations.},
     journal = {Portugaliae mathematica},
     pages = {185--204},
     publisher = {mathdoc},
     volume = {51},
     number = {2},
     year = {1994},
     zbl = {0807.20053},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1994__51_2_47075/}
}