Section LowerCentral.
Variable gT : finGroupType.
Implicit Types (A B : {set gT}) (G H : {group gT}).

Lemma lcn_bigdprod n I r P (F : I -> {set gT}) G :
\big[dprod/1]_(i <- r | P i) F i = G ->
\big[dprod/1]_(i <- r | P i) 'L_n(F i) = 'L_n(G).