1. R. Schulmann, A. J. Kox, M. Janssen, and J. Illy, eds., The Collected Papers of Albert Einstein, Vol. 8, The Berlin Years: Correspondence, 1914–1918, Princeton Univ. Press, Princeton, N. J. (1998); A. Beck and D. Howard, eds., The Collected Papers of Albert Einstein, Vol. 4, The Swiss Years: Writings, 1912–1914, Princeton Univ. Press, Princeton, N. J. (1996); M. Janssen, Ann. Phys. (8), 14, No. S1, 58 (2005).
2. Boston Stud. Phil. Sci.;M. Janssen,2007
3. M. Fierz and W. Pauli, Proc. Roy. Soc. London, Ser. A, 173, 211 (1939); N. Rosen, Phys. Rev., 57, 147, 150 (1940); A. Papapetrou, Proc. Roy. Irish Acad. Sect. A, 52, 11 (1948); S. N. Gupta, Phys. Rev., 96, 1683 (1954).
4. R. H. Kraichnan, Phys. Rev., 98, 1118 (1955).
5. M. Kohler, Z. Phys., 134, 286 (1953).