fact: Definition vitali_cover {R : realType} (E : set R) I (B : I -> set R) (D : set I) := (forall i, is_ball (B i)) /\ forall x, E x -> forall e : R, 0 < e -> exists i, [/\ D i, B i x & (radius (B i))%:num < e].
imports: mathcomp(all_ssreflect ssralg ssrnum ssrint interval) mathcomp(finmap fingroup perm rat) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality fsbigop) reals ereal signed topology numfun normedtype HB(structures) sequences esum measure real_interval realfun exp lebesgue_stieltjes_measure