The Brauer group is the group of classes of finite dimensional central simple algebras over 
with respect to a certain equivalence.
Brauer Group
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References
Hazewinkel, M. (Managing Ed.). Encyclopaedia of Mathematics: An Updated and Annotated Translation of the Soviet "Mathematical Encyclopaedia." Dordrecht, Netherlands: Reidel, p. 479, 1988.Referenced on Wolfram|Alpha
Brauer GroupCite this as:
Weisstein, Eric W. "Brauer Group." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/BrauerGroup.html