+- the main (principal) moments of inertia (in row <b>IX & IY & IZ</b>)
+
+\note The matrix of inertia is returned in the central coordinate
+ system (G, Gx, Gy, Gz) where G is the centre of mass of the system
+ and Gx, Gy, Gz the directions parallel to the X(1,0,0), Y(0,1,0), Z(0,0,1)
+ directions of the absolute cartesian coordinate system.
+
+\note There is always a set of axes for which the products of inertia
+ of a geometric system are equal to 0. These axes are the principal
+ axes of inertia. Their origin is coincident with the center of mass
+ of the system. The associated moments are called the principal moments
+ of inertia. The principal axes are not reported by this functionality.
+
+\br