1. also L. D. Landau and E. M. Lifshitz,Statistical Physics(Pergamon Press, London, 1958).
2. Strictly this integral is divergent but the divergent part disappears on taking the derivative, which is all that is required.
3. L. Spitzer, Jr.,Physics of Fully Ionized Gases(Interscience Publishers, Inc., New York, 1956).