1. Über die elastische Streuung von Elektronen in Argon und Neon;Kalckar;Mat-Fys. Medd. Dan. Vidensk. Selsk.,1933
2. On the Theory of the Catalysis of the Ortho-para Transformation by Paramagnetic Gases;Kalckar;Proc. Roy. Soc.,1935
3. On the Transmutation of Atomic Nuclei by Impact of Material Particles, Part I: General Theoretical Remarks;Bohr;Mat-Fys. Medd. Dan. Vidensk. Selsk.,1937
4. Note on Nuclear Photoejfect at High Energies;Kalckar;Phys. Rev.,1937
5. Note on Resonances in Transmutations of Light Nuclei;Kalckar;Phys. Rev.,1937