fact: Definition GI E s := forall z z', inc z E -> inc z' E -> (exists2 z'', inc z'' E & inc (J (J z z'') z') s) /\ (exists2 z''', inc z''' E & inc (J (J z''' z) z') s).
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)