  It is commonly stated in Newtonian Mechanics that the torque with respect to
the laboratory frame is equal to the torque with respect to the center of mass
frame plus a (R X F) factor, with "R" being the position of the center of mass
and "F" denoting the total external force. Although this assertion is true,
there is a subtlety in the demonstration that is overlooked in the textbooks.
In addition, it is necessary to clarify that if the reference frame attached to
the center of mass rotates with respect to certain inertial frame, the
assertion is not true any more.
