1. Nature, 144, 888 (1939) ; 146, 391 (1940).
2. Ann. der Phys., 17, 891 (1905). English translation in “The Principle of Relativity”, by A. Einstein and Others (Methuen, 1923).
3. Nature, 167, 680 (1951).
4. For example, Nature, 122, 673 (1928); 133, 818 (1934); 139, 784 (1937);
5. Mon. Not. Roy. Astro. Soc., 113, 393 (1953).