@article{10_4064_cm_9_1_1_31,
     author = {Roman Sikorski},
     title = {Algebra of formalized languages},
     journal = {Colloquium Mathematicum},
     pages = {1--31},
     publisher = {mathdoc},
     volume = {9},
     number = {1},
     year = {1962},
     doi = {10.4064/cm-9-1-1-31},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-9-1-1-31/}
}