12Dxx Real and complex fields

12D05  Polynomials: factorization
12D10  Polynomials: location of zeros (algebraic theorems), {For
               the analytic theory, See 26C10, 30C15}
12D15  Fields related with sums of squares (formally real fields,
               Pythagorean fields, etc.), See also {11Exx}
12D99  None of the above but in this section