1. The analogous formula in dislocation theory reads couple stress = δ (deformation energy)/δ (Cosserat-Nye structure curvature). Cf. e.g. Kröner, E.: Plastizität und Versetzungen. In: Sommerfeld, A.: Vorlesungen über theoretische Physik, Vol. 2, Chap. 9, 5th Ed. Leipzig: Akad. Verlagsges. 1964.
2. For a recent article on this subject containing also references to former works of Sciama, Kibble, Kröner, and others; cf. Hehl, F. : Abh. Braunschw. Wiss. Ges. 18, 98 (1966).
3. At least a in first approximation, neutrons, which, as is well known, can be described by a spinning field, fall like balls. But the accuracy of measurement is not too high. Cf. the article of Koester, L.: Z. Phys. 198, 187 (1967).
4. Sciama, D. W. : private communication.