theorem Th7:
  for L being meet-absorbing meet-commutative join-absorbing
meet-associative non empty LattStr, a, b, c being Element of L st a [= b & a
  [= c holds a [= b "/\" c
proof
  let L be meet-absorbing meet-commutative join-absorbing meet-associative
  non empty LattStr, a, b, c be Element of L;
  a "/\" a = a;
  hence thesis by Th5;
end;
