Let M be an A-module with a basis (ei)i∈J (finite or otherwise) whose indexing set J is totally ordered. For every integer p>0, let (eH)H∈Sp(J) be the corresponding basis of ∧p(M) (§ 7, no. 8). Let (xi)1≤i≤p be a sequence of p elements of M; let
xi=j∈J∑ξjiejfor i∈I={1,p}
and let X denote the matrix (ξji) of type (J,I). Then
x1∧x2∧⋯∧xp=H∈Fp(J)∑(detXH,I)eH.
where H runs through the set Fp(J) of subsets of J with p elements.
This follows immediately from formula (12) of no. 4 and formula (6) of no. 3.
Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.