[1] G. D. Birkhoff and R.E. Langer, Relativity and Modern Physics, Harvard University Press, Cambridge MA, 1923.
[2] G. B¨orner, The Early Universe, Facts and Fiction, Springer, Berlin, 2003.
[3] S. Carroll, Spacetime and Geometry, Addison Wesley, Boston MA, 2004.
[4] Deepmala and L.N. Mishra, Differential operators over modules and rings as a path to the generalized differential geometry, Facta Universitatis (Niˇs) Ser. Math. Inform. 30 (2015), 753-764.
[5] R. D’Inverno, Introducing Einstein’s Relativity, Oxford University Press, Oxford, 1992.
[6] K. Drachal, Advantages of generalizing manifold model in mechanics and cosmology, In M. Lieskovsk´y and M. Mokryˇs, (eds.), Proceedings in Advanced Research in Scientific Areas, The 1st Virtual International Conference, 1451-1453, EDIS – Publishing Institution of the University of ˇZilina, ˇZilina, 2012.
[7] K. Drachal, Introduction to d–spaces, Math. Aeterna 3(2013), 753-770.
[8] K. Drachal, Differential spaces and cosmological models, In S. Badura, M. Mokryˇs, and A. Lieskovsk´y, (eds.), Proceedings in Scientific Conference, SCIECONF 2014, 376-380, EDIS – Publishing Institution of the University of ˇZilina, ˇZilina, 2014.
[9] K. Drachal, Differential spaces and spacetime singularities: a current perspective, In press.
[10] G. F. R. Ellis and B. G. Schmidt, Classification of singular space–times, Gen. Rel. Grav. 10(1979), 989-997.
[11] S. W. Hawking and G. F. R. Ellis, The Large Scale Structure of Space–Time, Cambridge University Press, Cambridge, 1973.
[12] P. G. Fre, Gravity, a Geometrical Course, Springer, Berlin, 2013.
[13] M. Heller and W. Sasin, Structured spaces and their application to relativistic physics, J. Math. Phys. 36(1995), 3644-3662.
[14] J. T. Jebsen, ¨ Uber die allgemeinen kugelsymmetrischen L¨osungen der Einsteinschen Gravitationsgleichungen im Vakuum, Ark. Mat. Ast. Fys. 15(1921), 1-9.
[15] S. Krasnikov, Quasiregular singularities taken seriously, Preprint, arXiv:0909.4963.
[16] E. Minguzzi and M. Sanchez, The causal hierarchy of spacetimes, In H. Baum and D. Alekseevsky, (eds.), Recent Developments in Pseudo–Riemannian Geometry, 299-358, Eur. Math. Soc. Publ. House, Z¨urich,
2008.
[17] V. N. Mishra, Some Problems on Approximations of Functions in Banach Spaces, Indian Institute of Technology, Roorkee, 2007.
[18] C. W. Misner, K. S. Thorne, and J. A. Wheeler, Gravitation, W. H. Freeman and Company, New York, 1973.
[19] Z. Odrzyg´o´zd´z, Geometrical Properties of Quasi–regular Singularities, Warsaw University of Technology, Warsaw, 1996.
[20] A. R. Parry, A survey of spherically symmetric spacetimes, Anal. Math. Phys. 4(2014), 333-375.
[21] L. I. Piscoran and V. N. Mishra, Projectively flatness of a new class of (a ,b )-metrics, Georgian Math. Journal, In press. [22] R. Sikorski, Abstract covariant derivative, Colloq. Math. 18(1967), 251-272.
[23] R. Sikorski, Differential modules, Colloq. Math. 24(1972), 45-79.
[24] J. ´ Sniatycki, Orbits of families of vector fields on subcartesian spaces, Ann. Inst. Fourier 53(2003), 2257-2296.
[25] J. ´ Sniatycki, Differential Geometry of Singular Spaces and Reduction of Symmetry, Cambridge University Press, Cambridge, 2013.
[26] R. M. Wald, General Relativity, The University of Chicago Press, Chicago IL, 1984.
[27] J. Watts, Differential spaces, vector fields, and orbit–type stratifications, Preprint, arXiv:1104.4084
)