@article{SF_1989__39_2_134984,
     author = {M. Yamada and M.K. Sen},
     title = {P-regular semigroups.},
     journal = {Semigroup forum},
     pages = {157--178},
     publisher = {mathdoc},
     volume = {39},
     number = {2},
     year = {1989},
     zbl = {0664.20039},
     url = {http://geodesic.mathdoc.fr/item/SF_1989__39_2_134984/}
}