reserve p,q,r for FinSequence,
  x,y for object;

theorem Th29:
  for R being Relation, a,b being object st
  [a,b] in R holds a,b are_convertible_wrt R
proof
  let R be Relation, a,b be object;
  assume [a,b] in R;
  then R reduces a,b by Th15;
  hence thesis by Th25;
end;
