Fusion bases for affine Lie algebras
  Fusion coefficients for affine Lie algebras are fixed by the corresponding tensor-product coefficients and a set of threshold levels. It is shown how the information concerning the threshold level is coded in the fusion basis, which is a set of inequalities that completely describes the fusion coefficients. The construction of the su(2) fusion basis is presented in detail. 
Luc Begin, Chris Cummins and P. Mathieu