C*-algebras of labelled graphs II - Simplicity results
  We prove simplicity and pure infiniteness results for a certain class of labelled graph $C^*$-algebras. We show, by example, that this class of unital labelled graph $C^*$-algebras is strictly larger than the class of unital graph $C^*$-algebras. 
T. Bates and D. A. Pask