@article{SF_1978__16_134295,
     author = {A.H. Clifford},
     title = {Lectures in semigroups, by {M.} {Petrich.}},
     journal = {Semigroup forum},
     pages = {379--384},
     publisher = {mathdoc},
     volume = {16},
     year = {1978},
     url = {http://geodesic.mathdoc.fr/item/SF_1978__16_134295/}
}