Compare Figure 1 in Townsend, W.J.; Thornton, M.A. (2001). "Walsh spectrum computations using Cayley graphs". Proceedings of the 44th IEEE 2001 Midwest Symposium on Circuits and Systems (MWSCAS 2001). MWSCAS-01. Vol. 1. IEEE. pp. 110–113. doi:10.1109/mwscas.2001.986127. ISBN0-7803-7150-X.
Kunz, H.O. (1979). "On the Equivalence Between One-Dimensional Discrete Walsh–Hadamard and Multidimensional Discrete Fourier Transforms". IEEE Transactions on Computers. 28 (3): 267–8. doi:10.1109/TC.1979.1675334. S2CID206621901.