@article{AFM_1973_521-560_a18,
     author = {Magnus Steinby},
     title = {On pair algebras and state-information in automata},
     journal = {Annales Fennici Mathematici},
     year = {1973},
     volume = {521-560},
     doi = {10.5186/aasfm1973.542},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.5186/aasfm1973.542/}
}