reserve x,y,z for object, X for set, I for non empty set, i,j for Element of I,
    M0 for multMagma-yielding Function,
    M for non empty multMagma-yielding Function,
    M1, M2, M3 for non empty multMagma,
    G for Group-like multMagma-Family of I,
    H for Group-like associative multMagma-Family of I;

theorem
  for x3 being Element of M3 holds [3,x3] in FreeAtoms(<*M1,M2,M3*>)
proof
  let x3 be Element of M3;
  3 in {3} & x3 in the carrier of M3 by TARSKI:def 1;
  then [3,x3] in [: {3}, the carrier of M3 :] by ZFMISC_1:def 2;
  then [3,x3] in ([: {1}, the carrier of M1 :] \/ [: {2}, the carrier of M2 :])
    \/ [: {3}, the carrier of M3 :] by XBOOLE_0:def 3;
  hence thesis by Th14;
end;
