Discriminants, symmetrized graph monomials, and sums of squares   certificates
  Here we present certificates for 5 classes of 6-edged multigraphs whose symmetrized graph monomials may be represented as sum of squares, but not as linear combinations of partition square graphs. This is a complement to the results presented in Discriminants, symmetrized graph monomials, and sums of squares. 
Per Alexandersson
math.AG