@article{10_14708_cm_v22i1_6013,
     author = {D. M. Silberger},
     title = {How many unbordered words?},
     journal = {Commentationes Mathematicae},
     pages = { 143--145},
     publisher = {mathdoc},
     volume = {22},
     number = {1},
     year = {1980},
     doi = {10.14708/cm.v22i1.6013},
     language = {pl},
     url = {http://geodesic.mathdoc.fr/articles/10.14708/cm.v22i1.6013/}
}