1. Groot, S. R. DE and H. A. Tolhoek: β and γ ray spectroscopy (Ed. K. Siegbahn), Chap. 19 (III), p. 613. Amsterdam: North Holland Publishing Co. 1955.
2. Blin-Stoyle, R. J., M. A. Grace and H. Halbahn: βand γ ray spectroscopy (Ed. K. Siegbahn), Chap. 19 (II), p. 600. Amsterdam: North Holland Publishing Co. 1955.
3. Blin-Stoyle, R. J., M. A. Grace and H. Halban: Progress in Nuclear Physics III, p. 63 (Ed. O. Frisch ). London: Butterworth 1950.