1. Garrett Birkhoff and Saunders Mac Lane . 2010. A Survey of Modern Algebra ( 5 th ed.). A K Peters/CRC Press . Garrett Birkhoff and Saunders Mac Lane. 2010. A Survey of Modern Algebra (5th ed.). A K Peters/CRC Press.
2. David M. Bradley . 2005. Counting the Positive Rationals: A Brief Survey. arXiv:math/0509025 [math.HO] (Sept 2005 ), 1--7. David M. Bradley. 2005. Counting the Positive Rationals: A Brief Survey. arXiv:math/0509025 [math.HO] (Sept 2005), 1--7.
3. Recounting the Rationals
4. Lance Fortnow. 2004. Counting the Rationals Quickly. http://blog.computationalcomplexity.org/2004/03/counting-rationals-quickly.html (March 2004). Lance Fortnow. 2004. Counting the Rationals Quickly. http://blog.computationalcomplexity.org/2004/03/counting-rationals-quickly.html (March 2004).
5. Joachim von zur Gathen and Jürgen Gerhard . 2013. Modern Computer Algebra ( 3 rd ed.). Cambridge University Press . Joachim von zur Gathen and Jürgen Gerhard. 2013. Modern Computer Algebra (3rd ed.). Cambridge University Press.