. Then, N, ?) = ?xQ, ?xP ? ? ?xQ iff P ? ? Q with occ

N. If and . ?xp, then either M = ?yP 1 and P 1 ? ? P or M = x ? dom(?), ?(x)

N. If, M i ? ? P i or M = x ? dom(?), ?(x) = M 1 , M 2 and M i ? P i

N. If, ?. =-?-i-(-p-)-for-i, and . {1, 2}, then either M = ? i (P 1 ) and P 1 ? ? P or M = x ? dom(?), ?(x) = ? i

P. Straightforward, In the case of u = ?xv, we can apply Lemma 321. 1. x y for arbitrary variables x and y, 2. M µ?N

S. We-can, M. Easily, and . Iff, M (or (V U ) M , respectively) with U and V defined as above, We can formulate the following conjecture now

M. Intuitively, then M has the following property Let µ?M 1 ? M such that |M | ? > 1. Then either there is an address a for which M a = µ?M 1 or there is a (? N ) ? M and an address b such that N b = µ?M 1 . We may observe that the latter condition means that µ?M 1 is correct in M in the sense of Definition 83, Now we can state the following conjecture

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