Although Einstein did the preliminary analysis of the problem, it was London [6], in 1938, who developed the theory to its full extent, examining in detail the behaviour of the boson gas above and below the temperature TB. In his classic paper he explained, for example, why at temperatures above TB, one might neglect N0. He also derived expressions for the internal energy of the gas at temperatures above and below this point. In the former case, the energy may be obtained from the following integral: