Handbook of formal languages, vol. 1
Periodicity and the golden ratio
Theoretical Computer Science - Special issue: papers dedicated to the memory of Marcel-Paul Schützenberger
Introduction To Automata Theory, Languages, And Computation
Introduction To Automata Theory, Languages, And Computation
Locally periodic versus globally periodic infinite words
Journal of Combinatorial Theory Series A
Abelian Squares are Avoidable on 4 Letters
ICALP '92 Proceedings of the 19th International Colloquium on Automata, Languages and Programming
Problems in between words and abelian words: k-abelian avoidability
Theoretical Computer Science
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We consider the general problem when local regularity implies the global one in the setting where local regularity means the existence of a square of certain length in every position of an infinite word. The square can occur as centered or to the left or to the right from each position. In each case there are three variants of the problem depending on whether the square is that of words, that of abelian words or, as an in between case, that of so called k-abelian words. The above nine variants of the problem are completely solved, and some open problems are addressed in the k-abelian case. Finally, an amazing unavoidability result for 2-abelian squares is obtained.