Primitive of Reciprocal of x by x cubed plus a cubed squared

Theorem

 * $\displaystyle \int \frac {\mathrm d x} {x \left({x^3 + a^3}\right)^2} = \frac 1 {3 a^3 \left({x^3 + a^3}\right)} + \frac 1 {3 a^6} \ln \left({\frac {x^3} {x^3 + a^3} }\right)$