Links
[1] http://hootsgo.com/?q=node/6716
[2] http://www.cut-the-knot.org/Probability/ContinuousSampleSpaces.shtml
[3] http://www.cut-the-knot.org/Probability/GeometricProbabilities.shtml
[4] http://www.cut-the-knot.org/m/Probability/InfiniteDiscrete.shtml
[5] http://www.cut-the-knot.org/m/Probability/TwoCoprime.shtml