will be called “the interchanging [i, k] subconjunctivity (of order a).” The following fact, analogous to [3, Fact 1.41, characterizes the effect of an arbitrary subconjunctivity. Fact 1.1. Let S be an n x PZ matrix, M be a subset of (1, . . . , n>, m be the cardinal of M, D be an m x m nonsingular matrix, and T be the matrix obtained by applying to S the [M] subconjunctivity (of order n) defined by D. Then