reserve U1,U2,U3 for Universal_Algebra,
  n,m for Nat,
  o1 for operation of U1,
  o2 for operation of U2,
  o3 for operation of U3,
  x,y for set;
reserve a for FinSequence of U1,
  f for Function of U1,U2;
reserve E for Congruence of U1;

theorem
  f is_epimorphism implies QuotUnivAlg(U1,Cng(f)),U2 are_isomorphic
proof
  assume
A1: f is_epimorphism;
  take HomQuot(f);
  thus thesis by A1,Th20;
end;
