Section Chiefs.
Variable gT : finGroupType.
Implicit Types G H U V : {group gT}.

(* Specifications: *)
Lemma chief_factor_minnormal G V U :
chief_factor G V U -> minnormal (U / V) (G / V).
Lemma acts_irrQ G U V :
G \subset 'N(V) -> V <| U ->
acts_irreducibly G (U / V) 'Q = minnormal (U / V) (G / V).
Lemma chief_series_exists H G :
H <| G -> {s | (G.-chief).-series 1%G s & last 1%G s = H}.