Samuelson

http://highered.mcgraw-hill.com/sites/0072872071/student_view0/ Microeconomics, 18/e Samuelson

http://highered.mcgraw-hill.com/sites/0073126632/student_view0/ continuar aqui capitulo 21

http://www.mhhe.com/economics/mcconnellmacro15e/student/olc/discoverecon.mhtml McConnell 15 MacroEconomics

http://www.mhhe.com/economics/mcconnell15e/student/olc/discoverecon.mhtml McConnell 15 Economics