@article{SF_1979__17_134309,
     author = {K. Byleen},
     title = {Spirals of idemopotents from {P-semigroups.}},
     journal = {Semigroup forum},
     pages = {95--100},
     publisher = {mathdoc},
     volume = {17},
     year = {1979},
     zbl = {0398.20065},
     url = {http://geodesic.mathdoc.fr/item/SF_1979__17_134309/}
}