Code-equations/Gravitational-Potential-including-indirect-terms.md

@@ -57,8 +57,10 @@ To select this choice for a simulation in the config file:
     }
 ```
 
-## The indirect terms 
-Two terms in the potential accounts for the acceleration of the primary they come  from the acceleration  due respectively to the planet(s) and to the disk:
+## The potential due to indirect terms 
+We recall that we use a non inertial  frame : the origin of the
+system is centered on the primary body which is  
+accelerated by  the planet(s) and by the disk:
 
 $`\tilde \Phi_p = {{ G m_p} \over {r_p^3}}(\vec r_p \cdot \vec r)`$
 
@@ -68,7 +70,7 @@ planet and the star and a grid cell and the star
 
 $`\tilde \Phi_d =   \vec a  \cdot \vec r `$
 
-where $`\vec a$ is the acceleration of the primary due to the whole disk.
+where $`\vec a`$ is the acceleration of the primary due to the whole disk.
 
 When doing simulations in production mode such terms must be included in the computations. However, it may be useful to control the contribution from indirect terms. At this purpose the indirect terms may be de activated in the config file with the flag IndirectForces in the Referential group :