1. A. Einstein: The Meaning of Relativity (Princeton Univ. Press, Princeton, NJ 1950) pp.57, 82, 111
2. R.H. Dicke: The Theoretical Significance of Experimental Relativity (Gordon and Breach, New York 1965) pp.5, 8, 27
3. S.W. Hawking, W. Israel (eds.): General Relativity. An Einstein Centenary Survey (Cambridge Univ. Press, Cambridge 1979) pp.4,28,45,46, 55, 88, 90
4. C.M. Will: Theory and Experiment in Gravitational Physics (Cambridge Univ. Press, Cambridge 1981) pp.3,24,35,171,176,184, 222, 256
5. A. Pais: Subtle is the Lord ( Clarendon, Oxford 1982 ) p. 178