On the Uniqueness of the Non-Abelian Gauge Theories in Epstein-Glaser   Approach to Renormalisation Theory
  We generalise a result of Aste and Scharf saying that, under some reasonable assumptions, consistent with renormalisation theory, the non-Abelian gauge theories describes the only possibility of coupling the gluons. The proof is done using Epstein-Glaser approach to renormalisation theory. 
Dan Radu Grigore