An algebraic technique which maps elements from distinct finite rings into subsets of another finite ring is defined, and a method for combining elements from distinct finite rings is demonstrated. The connection between this mapping and the constructing of confounding plans for the mixed factorial experiment with any number of factors at any number of levels is established, as well as the limitation of the procedure.
"A General Approach to Confounding Plans in Mixed Factorial Experiments when the Number of Levels of a Factor is any Positive Integer." Ann. Statist. 2 (3) 579 - 585, May, 1974. https://doi.org/10.1214/aos/1176342720