theorem
  for A being Universal_Algebra, B being strict non-empty MSSubAlgebra
  of MSAlg A st the carrier of MSSign A = {0} holds 1-Alg B is SubAlgebra of A
proof
  let A be Universal_Algebra , B be strict non-empty MSSubAlgebra of MSAlg A;
  assume the carrier of MSSign A = {0};
  then MSAlg (1-Alg B) = the MSAlgebra of B by Th26;
  hence thesis by Th16;
end;
