1. Seyfried, P.: Proc. Intern. Conf. on Prescision Measurements and Fundamental Constants, Gaithersburg 1981 (to be published)
2. Ando, M., Bailey, D., Hart, M.: Acta Crystallogr. A34, 484 (1978)
3. Becker, P., Dorenwendt, K., Ebeling, G., Lauer, R., Lucas, W., Probst, R., Rademacher, H.-R., Reim, G., Seyfried, P., Siegert, H.: Phys. Rev. Lett.46, 1540 (1981)
4. Cullity, B.D.: Elements of x-ray Diffraction. 3rd Edn. London: Addison-Wesley 1967
5. Siegert, H., Becker, P.: PTB. Bericht APh 21, Physikalisch-Technische Bundesanstalt, Braunschweig (1984)