http://www.cut-the-knot.org/m/Probability/SymmetryPrinciple.shtml [2]
http://www.cut-the-knot.org/Probability/dAlembert.shtml [3]
http://www.cut-the-knot.org/m/Probability/RandomPointsOnSegment.shtml [4]
Links[1] http://hootsgo.com/?q=node/6726 [2] http://www.cut-the-knot.org/m/Probability/SymmetryPrinciple.shtml [3] http://www.cut-the-knot.org/Probability/dAlembert.shtml [4] http://www.cut-the-knot.org/m/Probability/RandomPointsOnSegment.shtml