Talk:Sigma-ring
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Rudin's second book, Real and Complex Analysis, uses sigma-algebras; there is a note on page 397 (3rd ed.) about sigma-rings vs sigma-algebras. --Keith111 14:54, 10 September 2006 (UTC)
He says essentially that sigma-rings provide greater generality but require a fussier definition of measurability, and in classical applications the measurability of the universal set (the set of all real numbers, for instance) is "more or less automatic" (in which case the sigma-ring is closed under absolute complements and is hence a sigma-algebra). --Keith111 22:24, 15 October 2006 (UTC)
