Hong, G., Schautz, F., & Dolg, M. (1999). Ab Initio Study of Metal-Ring Bonding in the Bis(?6-benzene) lanthanide and -actinide Complexes M(C6H6)2 (M = La, Ce, Nd, Gd, Tb, Lu, Th, U). Journal of the American Chemical Society, 121, 1502-1512.