| perm(x, y), perm(a ' + y, ins≤(a, y)), perm(a ' + x, ins≤(a, x)), perm(ins≤(a, x), a ' + x), perm(ins≤(a, y), a ' + y), perm(y, x) ⊦ perm(ins≤(a, x), ins≤(a, y)), perm(ins≤(a, y), ins≤(a, x)) |
⊦ perm(a ' + x, a ' + y) ↔ perm(x, y)
perm(a ' + x, a ' + y), perm(a ' + y, ins≤(a, y)), perm(a ' + x, ins≤(a, x)), perm(ins≤(a, x), a ' + x), perm(ins≤(a, y), a ' + y), perm(y, x) ⊦ perm(ins≤(a, x), ins≤(a, y)), perm(ins≤(a, y), ins≤(a, x))
Used terms: a, x, y