訂正日: 2006/09/29訂正理由: -訂正箇所: 引用文献情報訂正内容: Right : [1] S. A. Amitsur, Embeddings in Matrix rings, Pacific J. Math., 36 (1971), 21-29. [2] H. Bass, Lectures on topics in algebraic K-theory, Tata Institute, Bombay, 1967. [3] M. Auslander and O. Goldman, The Brauer group of a commutative ring, Trans. Amer. Math. Soc., 97 (1960).