References
- W. H. Gustafson, What is the probability that two group elements commute? Amer. Math. Monthly 80 (1973) 1031–1034; available at http://dx.doi.org/10.2307/2318778.
- D. MacHale, Commutativity in finite rings. Amer. Math. Monthly 83 (1975) 30–32; available at http://dx.doi.org/10.2307/2318829.
- B. Givens, The probability that two semigroup elements commute can be almost anything. College Math J. 39 (2008) 399–400.
- V. Ponomarenko and N. Selinski, Two semigroup elements can commute with any positive rational probability. College Math J. 43 (2012) 334–336; available at http://dx.doi.org/10.4169/college.math.j.43.4.334.