Section Clifford.
Variables (gT : finGroupType) (G H : {group gT}).
Hypothesis nsHG : H <| G.
Variables (n : nat) (rG : mx_representation F G n).
Let sHG := normal_sub nsHG.
Let nHG := normal_norm nsHG.
Let rH := subg_repr rG sHG.
Hypothesis irrG : mx_irreducible rG.

Lemma Clifford_basis M : mxsimple rH M ->
{X : {set gT} | X \subset G &
let S := \sum_(x in X) M *m rG x in S :=: 1%:M /\ mxdirect S}%MS.