| Pelem ^*(b, c), Pelem(a, c0), rtc(n0, Pelem)(c0, b), Pelem ^*(c0, c) ⊦ Pelem ^*(a, c) |
⊦ Pelem ^*(a, b) ↔ (∃ n. rtc(n, Pelem)(a, b))
Pelem ^*(b, c), Pelem(a, c0), rtc(n0, Pelem)(c0, b), ∃ n. rtc(n, Pelem)(c0, c) ⊦ Pelem ^*(a, c)
Used terms: c, c0, Pelem