@article{SF_1977__15_134266,
     author = {R.H. Oehmke},
     title = {The semigroup of a strongly connected automaton.},
     journal = {Semigroup forum},
     pages = {351--356},
     publisher = {mathdoc},
     volume = {15},
     year = {1977},
     zbl = {0383.20056},
     url = {http://geodesic.mathdoc.fr/item/SF_1977__15_134266/}
}