1. Class Field Theory;Artin,1961
2. Hereditarily Pythagorean fields, infinite Harrison-primes and sums of 2nth powers;Becker;Bull. Amer. Math. Soc.,1978
3. E. Becker, “Hereditarily Pythagorean Fields and Orderings of Higher Type,” JMPA Lecture Notes, Rio de Janeiro.
4. The ordinary quaternions over a Pythagorean field;Fein,1976
5. B. Fein and M. Schacher, Strong crossed product division algebras,Comm. Algebra, in press.