Primitive of Reciprocal of x squared by x fourth minus a fourth

Theorem

 * $\displaystyle \int \frac {\mathrm d x} {x^2 \left({x^4 - a^4}\right)} = \frac 1 {a^4 x} + \frac 1 {4 a^5} \ln \left\vert{\frac {x - a} {x + a} }\right\vert + \frac 1 {2 a^5} \arctan \frac x a + C$