theorem
  x is being_a_sum_of_amalgams_of_squares & y is generated_from_squares
  implies x+y is generated_from_squares
proof
  assume that
A1: x is being_a_sum_of_amalgams_of_squares and
A2: y is generated_from_squares;
  x is generated_from_squares by A1,Th1;
  hence thesis by A2,Lm64;
end;
