1. Arnowitt, R., Deser, S., Misner, C.W.: In: Witten, L. (ed.) Gravitation: An Introduction to Current Research. Wiley, New York (1962)
2. Ashtekar, A.: In: Bergmann, P.G., V. de, Sabbata (eds.) Cosmology and Gravitation. Plenum, New York (1980)
3. Bergmann, P.G., Thomson, R.: Phys. Rev. 89, 401 (1953)
4. Blagojević, M., Vasilić, M.: Class. Quantum Gravity 5, 1241 (1988)
5. Belfer Gradute School of Science (Monographs Series);P.A.M. Dirac,1964