Theorem 1

Suppose that the $A$-module $E$ admits a basis $(x_i)_{i \in L}$, the set of indices $L$ being endowed with a total ordering. For every finite subset $H$ of $L$, put $x_H = \rho(x_{h_1}) \rho(x_{h_2}) \ldots \rho(x_{h_q})$, where $(h_1, \ldots, h_q)$ is the strictly increasing sequence of the elements of $H$. Then the elements $x_H$ form a basis of the $A$-module $C(Q)$.