1. Fricke, B.: Struct. Bond. 21, 89–144 (1975)
2. Pyykkö, P.: Adv. Quant. Chem. 11, 353–409 (1978)
3. Pyykkö, P.: Chem. Rev. 88, 563–594 (1988)
4. Pyykkö, P., Desclaux, J.P.: Acc. Chem. Res. 12, 276–281 (1979)
5. Balasubramanian, K., Pitzer, K.S.: Adv. Chem. Phys. 67, 287–319 (1987)