A presentation of the trace algebra of three 3x3 matrices
  The trace algebra C_{nd} is generated by all traces of products of d generic n x n matrices. Minimal generating sets of C_{nd} and their defining relations are known for n < 3 and n = 3, d=2. This paper states a minimal generating set and their defining relations for n=d=3. Furthermore the computations yield a description of C_{33} as a free module over the ring generated by a homogeneous system of parameters. 
Torsten Hoge
math.RA math.AC