Nicholson's "Microeconomic Theory: Basic Principles and Extensions, 9th edition" is a tried-and-true, well-known and respected market-leading text. Applauded for providing the most clear and accurate presentation of advanced microeconomic concepts, it offers an ideal level of mathematical rigor for upper level undergraduate students and beginning graduate students. It gives students the opportunity to work directly with theoretical tools, real-world applications, and cutting edge developments in the study of microeconomics. Text is solid, rigorous, comprehensive, and is sensibly challenging for students, best serving students with a mathematics background.