Krzysztof Bolejko is an Assistant Professor at the Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Poland. His area of research is cosmology, in particular applications of inhomogeneous cosmological models, study of light propagation, backreaction effects, and faster than light mechanisms. Andrzej Krasiński is an Associate Professor at Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Poland. He is currently doing research in gravitation theory, in particular exact solutions of Einstein's equations and inhomogeneous cosmological models. He is also a member of the Editorial Board of the GRG Journal, where he is the editor of the 'Golden Oldies' series of reprints of classical papers on relativity. Charles Hellaby is an Associate Professor in the Department of Mathematics and Applied Mathematics, University of Cape Town, South Africa. His research interest is cosmology and relativity, particularly properties and applications of inhomogeneous metrics, and relating observations to cosmological models. Marie-Noëlle Célérier is a Researcher at the Laboratoire Univers et Théories (LUTH), Observatoire de Paris-Meudon, France. Her two main fields of interest are scale relativity and inhomogeneous cosmology.