La Classification Mathématique par matières 2000 Mathematics subject Classification 2000 Query : CC = 11E81 11-XX Number theory 11E81 Algebraic theory of quadratic forms; Witt groups and rings [See also 19G12, 19G24] 19-XX $K$-theory [See also 16E20, 18F25] 19G12 Witt groups of rings [See also 11E81] 19G24 L-theory of group rings [See also 11E81] Keyword : Back to the Mathematics Subject Classification (version 2000)