Yuan Gao Kai Salomaa Sheng Yu The State Complexity of Two Combined Operations: Star of Catenation and Star of Reversal. 75-89 2008 83 Fundam. Inform. 1-2 http://iospress.metapress.com/content/v030j74w24l01141/ db/journals/fuin/fuin83.html#GaoSY08