@article{SEMR_2005_2_a1,
     author = {A. \`E. Frid},
     title = {A~lower bound for the arithmetical complexity of {Sturmian} words},
     journal = {Sibirskie \`elektronnye matemati\v{c}eskie izvesti\^a},
     pages = {14--22},
     publisher = {mathdoc},
     volume = {2},
     year = {2005},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/SEMR_2005_2_a1/}
}