refine ⟨fun h C hC hCU ↦ ?_, fun h ↦ ?_⟩
ι : Type u_1
α : Type u_2
M : Matroid α
B I J X X' Y Y' F : Set α
Xs Ys Js Is : ι → Set α
i j : ι
e f : α
hXs : ∀ (i : ι), Xs i ⊆ M.E
hdj : Pairwise (Disjoint on Xs)
⊢ M.SkewFamily Xs ↔ ∀ (C : Set α), M.Circuit C → C ⊆ ⋃ i, Xs i → ∃ i, C ⊆ Xs i
case refine_1
ι : Type u_1
α : Type u_2
M : Matroid α
B I J X X' Y Y' F : Set α
Xs Ys Js Is : ι → Set α
i j : ι
e f : α
hXs : ∀ (i : ι), Xs i ⊆ M.E
hdj : Pairwise (Disjoint on Xs)
h : M.SkewFamily Xs
C : Set α
hC : M.Circuit C
hCU : C ⊆ ⋃ i, Xs i
⊢ ∃ i, C ⊆ Xs i

case refine_2
ι : Type u_1
α : Type u_2
M : Matroid α
B I J X X' Y Y' F : Set α
Xs Ys Js Is : ι → Set α
i j : ι
e f : α
hXs : ∀ (i : ι), Xs i ⊆ M.E
hdj : Pairwise (Disjoint on Xs)
h : ∀ (C : Set α), M.Circuit C → C ⊆ ⋃ i, Xs i → ∃ i, C ⊆ Xs i
⊢ M.SkewFamily Xs