1. See, for instance, C. W. Misner, K. S. Thorne and J. A. Wheeler, Gravitation (Freeman and Co., San Francisco, 1973).
2. H. Weyl, Sitzungesber Deutsch. Akad. Wiss. Berli 465 (1918);
3. H. Weyl, Space, Time, Matter (Dover, New York, 1952).
4. A nice account of Weyl’s ideas as well as the refutation of his gravitational theory may be found in W. Pauli, Theory of Relativity (Dover, New York, 1981).
5. Gauge theory: Historical origins and some modern developments