R. Blecksmith et al., A CONSTRUCTIVE THEORY OF TRIPLE AND QUINTUPLE PRODUCT IDENTITIES OF THE 2ND DEGREE, Mathematics of computation, 67(222), 1998, pp. 797-814
The groundwork for a theory of quadratic identities involving the clas
sical triple and quintuple products is layed. The approach is through
the study and use of affine maps that act oh indexing lattices associa
ted with the terms (double sums) in the given identity. The terms of t
he identity are found to be connected by the invariant of a ternary qu
adratic form.