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Lecture Notes in Computer Science
The concatenation product is one of the most important operations on regular languages. Its study requires sophisticated tools from algebra, finite model theory and profinite topology. This paper surveys research advances on this topic over the last fifty years. The concatenation product plays a key role in two of the most important results of automata theory: Kleene's theorem on regular languages  and Schützenberger's theorem on star-free languages  . This survey article surveys thedoi:10.1007/978-3-642-21493-6_3 fatcat:2gqznrmyqzbkjbjumq4xf757nm