@article{SF_1995__51_1_135399,
     author = {C.M. Campbell and E.F. Robertson and R.M. Thomas and N. Ruskuc},
     title = {Reidemeister- {Schreier} type rewriting for semigroups.},
     journal = {Semigroup forum},
     pages = {47--62},
     publisher = {mathdoc},
     volume = {51},
     number = {1},
     year = {1995},
     zbl = {0833.20069},
     url = {http://geodesic.mathdoc.fr/item/SF_1995__51_1_135399/}
}