Circular convolution is commutative?

[Chris Warburton]

We shouldn't be using a commutative operation. According to:

Cox, G., Kachergis, G., Recchia, G., & Jones, M. N. (2011).
Towards a scalable holographic word-form representation.
Behavior Research Methods, 43, 602-615.

They apply a "random" but invertible permutation before doing the
circular convolution, to force it to be non-commutative.

Compare their formulation to our original source.