|- (!A. RESTRICT [] A = []) /\ (!x t A. RESTRICT (CONS x t) A = ((x IN A) => (CONS x (RESTRICT t A)) | (RESTRICT t A)))
|- !A. RESTRICT [] A = []
|- !s t A. RESTRICT (APPEND s t) A = APPEND (RESTRICT s A) (RESTRICT t A)
|- !s. RESTRICT s {} = []
|- !s A B. RESTRICT (RESTRICT s A) B = RESTRICT s (A INTER B)
|- !A s. LENGTH (RESTRICT s A) <= LENGTH s
|- !A s a. ~(LENGTH (RESTRICT s A) = LENGTH (CONS a s))
|- !a A s. ~(RESTRICT s A = CONS a s)