⊦ bag0 ⊆ bag1 ↔ (∀ a. count(a, bag0) ≤ count(a, bag1))
∀ a. count(a, bag1) ≤ count(a, bag0), bag0 ⊆ bag1 ⊦ count(a, bag0) = count(a, bag1)
Used terms: bag0, bag1