@article{SF_1991__43_3_135114,
     author = {P.V. Ramana Murty and S. Hanumantha Rao},
     title = {On a problem in poe-semigroups.},
     journal = {Semigroup forum},
     pages = {260--262},
     publisher = {mathdoc},
     volume = {43},
     number = {3},
     year = {1991},
     zbl = {0732.06008},
     url = {http://geodesic.mathdoc.fr/item/SF_1991__43_3_135114/}
}