Primitive of x squared over x fourth minus a fourth

Theorem

 * $\displaystyle \int \frac {x^2 \ \mathrm d x} {x^4 - a^4} = \frac 1 {4 a} \ln \left\vert{\frac {x - a} {x + a} }\right\vert + \frac 1 {2 a^3} \arctan \frac x a + C$