Arguments cent_mxP {m n B R}.

Lemma mxdirect_sums_center (I : finType) m n (R : 'A_(m, n)) R_ :
(\sum_i R_ i :=: R)%MS -> mxdirect (\sum_i R_ i) ->
(forall i : I, mx_ideal R (R_ i)) ->
('Z(R) :=: \sum_i 'Z(R_ i))%MS.