 reserve A,B,O for Ordinal,
      n,m for Nat,
      a,b,o for object,
      x,y,z for Surreal,
      X,Y,Z for set,
      Inv,I1,I2 for Function;

theorem Lm3:
  x*y ==0_No iff x == 0_No or y == 0_No by SURREALR:72,74;
