reserve x,y,z for Real,
  R for real non empty RelStr,
  a,b for Element of R;
reserve C for non empty set,
  c for Element of C,
  f,g for Membership_Func of C,
  s,t for Element of FuzzyLattice C;

theorem
  s <<= t iff for c holds @s.c <= @t.c
proof
  (C,@s)@ = s & (C,@t)@ = t;
  hence thesis by Th16;
end;
