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 Th17:
  x ==> y implies x >>01<< y
  proof
    assume
A1: x ==> y;
    take y;
    thus x =01=> y & y =01=> y by A1;
  end;
