1. W. Heisenberg, Z. Phys. A-Hadron Nucl. 120, 513 (1943)
2. W. Heisenberg, Z. Phys. A-Hadron Nucl. 120, 673 (1943)
3. W. Heisenberg, Z. Naturforsch. Pt A 1, 608 (1946)
4. C. Moeller, Mat. Fys. Medd. Dan. Vid. 23, N1 (1945)
5. C. Moeller, Mat. Fys. Medd. Dan. Vid. 22, N19 (1946)