theorem LmA:
  x <> y & (for a,b holds a ==> b iff a = x)
  implies y is normform & x is normalizable
  proof
    assume
Z0: x <> y;
    assume
Z2: for a,b holds a ==> b iff a = x;
    thus y is normform by Z0,Z2;
    take y; thus y is normform by Z0,Z2;
    thus thesis by Z2,Th2;
  end;
