∀n1,XT1. ❪G,L❫ ⊢ T1 ➡[n1,h] XT1 → ∀n2,XT2. ❪G,L❫ ⊢ T2 ➡[n2,h] XT2 →
∀L1. ❪G,L❫ ⊢ ➡[h] L1 → ∀L2. ❪G,L❫ ⊢ ➡[h] L2 →
∃∃T. ❪G,L1❫ ⊢ XT1 ➡*[n2-n1,h] T & ❪G,L2❫ ⊢ XT2 ➡*[n1-n2,h] T.
∀n1,XT1. ❪G,L❫ ⊢ T1 ➡[n1,h] XT1 → ∀n2,XT2. ❪G,L❫ ⊢ T2 ➡[n2,h] XT2 →
∀L1. ❪G,L❫ ⊢ ➡[h] L1 → ∀L2. ❪G,L❫ ⊢ ➡[h] L2 →
∃∃T. ❪G,L1❫ ⊢ XT1 ➡*[n2-n1,h] T & ❪G,L2❫ ⊢ XT2 ➡*[n1-n2,h] T.