Following ref 15 and without loss of generality, we assume in the following that we are in the principal frame of the rigid body, where by an appropriate translation and rotation the center of mass has been placed at the origin and the tensor of inertia is diagonal. The pseudo tensor of inertia is then also diagonal, X = M diag (a 2 , b 2 , c 2 , 1). We define the diagonal matrix D = ( X/M ) 1/2 = diag (a, b, c, 1) and vectors qi that satisfy ri = Dq i .