reserve a,a1,a2,b,c,d for Ordinal,
  n,m,k for Nat,
  x,y,z,t,X,Y,Z for set;
reserve f,g for Function;
reserve A,B,C for array;
reserve O for connected non empty Poset;
reserve R,Q for array of O;
reserve T for non empty array of O;
reserve p,q,r,s for Element of dom T;

theorem Th66:
  p in q implies (T,p,q)incl.(p,q) = [p,q]
  proof assume
    p in q; then
    p c= q by ORDINAL1:def 2;
    hence thesis by Th62;
  end;
