New representation results for three families of regular languages are stated, using a special kind of shuffle operation, namely the synchronized shuffle. First, it is proved that the family of regular star languages is the smallest family containing the language (a + bc) * and closed under synchronized shuffle and length preserving morphism. The second representation result states that the family of εfree regular languages is the smallest family containing the language (a + bc) * d and closed

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... nder synchronized shuffle, union and length preserving morphism. At last, it is proved that Reg is the smallest family containing the two languages (a + bb) * and a+(ab) + , closed under synchronized shuffle, union and length preserving morphism.