@article{SF_1976__13_134216,
     author = {J. Fountain},
     title = {Right {PP} monoids with central idempotents.},
     journal = {Semigroup forum},
     pages = {229--238},
     publisher = {mathdoc},
     volume = {13},
     year = {1976},
     zbl = {0353.20051},
     url = {http://geodesic.mathdoc.fr/item/SF_1976__13_134216/}
}