1. Lecture Notes in Mathematics;D. Anderson,1979
2. Lecture Notes in Mathematics;A. Bak,1976
3. Bak, A., Scharlau, W.: Grothendieck and Witt groups of orders and finite groups. Invent. Math.23, 207?240 (1974)
4. Lecture Notes in Mathematics;G. Carlsson,1979
5. Cassels, J.W.S., Fröhlich, A.: Algebraic Number Theory. Washington: Thompson, 1967