1. , , , and , in: Vacuum Ultraviolet Radiation Physics, Ed. , and , Vieweg/Pergamon, Braunschweig 1974 (p. 344).
2. in: Vacuum Ultraviolet Radiation Physics, Ed. , and , Vieweg/Pergamon, Braunschweig 1974 (p. 317).
3. , , and , in: Vacuum Ultraviolet Radiation Physics, Ed. , and , Vieweg/Pergamon, Braunschweig 1974 (p. 341).
4. and , private communication.