Microeconomic Theory by Andreu Mas-Colell, Michael D. Whinston, and Jerry R. Green is the standard US graduate level microeconomics textbook.
First published in 1995, the book consists of five parts: Part I: Individual Decision-Making; Part II: Game Theory; Part III: Market Equilibrium and Market Failure; Part IV: General Equilibrium; Part V: Welfare Economics and Incentives.
The book provides a rigorous (mathematical) and lengthy (nearly 1000 pages) treatment of the standard microeconomic theorems and their proofs.
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