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

Theorem

 * $\ds \int \frac {\d x} {x \paren {x^3 + a^3}^2} = \frac 1 {3 a^3 \paren {x^3 + a^3} } + \frac 1 {3 a^6} \ln \size {\frac {x^3} {x^3 + a^3} }$