Deriving identities for Wigner {nj}-symbols
  We show how a simple and elegant graphical notation can be used to derive the Biedenharn-Elliot identity for the 6j-symbol and we demonstrate how the same technique can be applied to obtain new identities for the 6j. We then employ the same method also in the context of 4D spin-foam gravity and propose an analogous identity for the 15j-symbol. 
Gianluca Delfino
gr-qc