@article{SF_1988__37_1_134913,
     author = {H.J. Shyr and M. Ito and M. Katsura and S.S. Yu},
     title = {Automata accepting primitive words.},
     journal = {Semigroup forum},
     pages = {45--52},
     publisher = {mathdoc},
     volume = {37},
     number = {1},
     year = {1988},
     zbl = {0646.20055},
     url = {http://geodesic.mathdoc.fr/item/SF_1988__37_1_134913/}
}