I am grateful to Emanuele Berti, John L. Friedman, Wlodek
Kluzniak, Kostas D. Kokkotas, and Luciano Rezzolla for a careful
reading of the manuscript and for many valuable comments. Many
thanks to Dorota Gondek-Rosinska and Eric Gourgoulhon for
comments and for supplying numerical results obtained with the
Lorene/rotstar code, that were used in the comparison in
Table
2
. I am also grateful to Marcus Ansorg for discussions and to all
authors of the included figures for granting permission for
reproduction. This work was supported, in part, by the EU
Programme ``Improving the Human Research Potential and the
Socio-Economic Knowledge Base'' (Research Training Network
Contract HPRN-CT-2000-00137), KBN-5P03D01721, and the Greek GSRT
Grant EPAN-M.43/2013555.