reserve X for ARS, a,b,c,u,v,w,x,y,z for Element of X;
reserve i,j,k for Element of ARS_01;
reserve l,m,n for Element of ARS_02;
reserve A for set;

theorem LemN1:
  x is normform & x =*=> y implies x = y
  proof
    assume
A1: x is normform;
    assume
A2: x =*=> y;
A4: not x =+=> y by A1;
    thus x = y by A2,A4,LemN;
  end;
