Hello, In the low temp. limit of Debye law for specific heat, we encounter the following integral: ∫(x4 ex)/(ex-1)2 dx, from 0 to ∞. The result is 4∏2/15. I have searched and found this to be related to zeta function but zeta functions do not have ex in the numerator so I am unable to evaluate the integral using them. Any help?