S. W. Goode, J. Wainwright: Isotropic Singularities in Cosmological Models. In: Class. Quantum Grav. 2. Jahrgang, 1985, S.99–115, doi:10.1088/0264-9381/2/1/010.
R. P. A. C. Newman: On the Structure of Conformal Singularities in Classical General Relativity. In: Proc. R. Soc. Lond. A. 443. Jahrgang, 1993, S.473–492, doi:10.1098/rspa.1993.0158.
K. Anguige, K. P. Tod: Isotropic Cosmological Singularities I. Polytropic Perfect Fluid Spacetimes. In: Ann. Phys. N.Y. 276. Jahrgang, 1999, S.257–293, doi:10.1006/aphy.1999.5946.
W. C. Lim, H. van Elst, C. Uggla and J. Wainwright: Asymptotic Isotropization in Inhomogeneous Cosmology. In: Phys. Rev. D. 69. Jahrgang, 2004, S.103507 (1–22), doi:10.1103/PhysRevD.69.103507.
R. Penrose: Difficulties with Inflationary Cosmology. In: E. J. Fergus (Hrsg.): Proc. 14th Texas Symp. on Relativistic Astrophysics. NY Academy of Sciences, New York 1989, S. 249–264, doi:10.1111/j.1749-6632.1989.tb50513.x