 As in LK, proofs constructed in NK are represented as trees with the proof’s conclusion sitting at the root of the tree, and the problem’s assumptions sitting at the leaves. (Proofs are also typically given as sequences of judgements, Γ ⊢ α, running from the top to the bottom of the printed page.) Here is a natural deduction proof tree of ∃xR(x) from ∀x(P(x) ∨ Q(x)), ∀x(P(x) ⊃ R(x)) and ∀x(Q(x) ⊃ R(x)):