  Higher order corrections are obtained for the perihelion precession in binary
systems like OJ287, Sagittarius A*-S2 and H1821+643 using both the
Schwarzschild metric and the Kerr metric to take into account the spin effect.
The corrections are performed considering the third root of the motion equation
and developing the expansion in terms of $\epsilon \equiv
r_s/\left(a(1-e^2)\right)$ and $\epsilon^{*} \equiv \left(1- \frac{2 \alpha
E'}{cJ}\right) \epsilon $.The results are compared with those obtained in a
previous paper.
