theorem
  F is atomic implies not H is_immediate_constituent_of F
proof
  assume F is atomic;
  then F.1 <> 2 & F.1 <> 3 & F.1 <> 4 & F.1 <> 5 & F.1 <> 0 & F.1 <> 1 by Lm9;
  hence thesis by Th12;
end;
