1. J. A. Wheeler, in: Relativity, Groups, and Topology, ed. B.S. and C. M. DeWitt (Gordan and Breach, New York 1964); S. W. Hawking, Nuclear Phys. B 114, 349 (1978).
2. A. A. Kirillov and E. P. Savelova, Grav. Cosmol. 19, 92 (2013); E. P. Savelova, Grav. Cosmol. 19, 101 (2013).
3. A. A. Kirillov and E. P. Savelova, Yad. Fiz. and Engineering 4, 932 (2013) [in Russian], arXiv: 1204.0351; E. P. Savelova, On possible origin of an anisotropy in the speed of light in vacuum, arXiv: 1405.1977; A. A. Kirillov and E. P. Savelova, On the possibility of generation of an artificial wormhole, arXiv: 1405.3171; A. A. Kirillov and E. P. Savelova, Effective action for a free scalar field in the presence of spacetime foam, arXiv: 1405.5074.
4. A. A. Kirillov and E. P. Savelova, Grav. Cosmol. 14, 256 (2008); A. A. Kirillov and E. P. Savelova, Phys. Lett. B 660, 93 (2008).
5. A. A. Kirillov and E. P. Savelova, Mon. Not. RAS 412, 1710 (2011).