Ladder operators for Szeg\H{o} polynomials and related biorthogonal   rational functions
  We find the raising and lowering operators for orthogonal polynomials on the unit circle introduced by Szeg\H{o} and for their four parameter generalization to ${}_4\phi_3$ biorthogonal rational functions on the unit circle. 
Mourad E. H. Ismail, Mizan Rahman