reserve a for set,
  i for Nat;

theorem Th7:
  for U1,U2 being Universal_Algebra st U1 is SubAlgebra of U2 holds
  MSSign U1 = MSSign U2
proof
  let U1,U2 be Universal_Algebra;
  set ff2 = dom signature(U1)-->z, gg2 = dom signature(U2)-->z;
  reconsider ff1 = (*-->0)*(signature U1) as Function of dom signature(U1), {0
  }* by MSUALG_1:2;
  reconsider gg1 = (*-->0)*(signature U2) as Function of dom signature(U2), {0
  }* by MSUALG_1:2;
  assume U1 is SubAlgebra of U2;
  then
A1: U1,U2 are_similar by UNIALG_2:13;
A2: MSSign U1 = ManySortedSign (#{0},dom signature(U1),ff1,ff2#) & MSSign U2
  = ManySortedSign (#{0},dom signature(U2),gg1,gg2#) by MSUALG_1:10;
  thus thesis by A1,A2;
end;
