[BS]
Robert G. Bartle and Donald R. Sherbert, Introduction to Real Analysis, 3rd ed., John Wiley & Sons Inc., New York, 2000.
http://giam.southernct.edu/GIAM/.http://www.people.vcu.edu/~rhammack/BookOfProof/.http://ramanujan.math.trinity.edu/wtrench/texts/TRENCH_REAL_ANALYSIS.PDF.