Fusion Rules for the q-deformed Vertex Operators of U_q(sl(2)^)
  We analyze the properties of the q-vertex operators of U_q(sl(2)^) introduced by Frenkel and Reshetikhin. As the condition for the null vector decoupling, we derive the existence condition of the q-vertex operators ( the fusion rules ). 
H. Awata and Y. Yamada