1. P.C.W. Davies: That mysterious flow, Sci. Am. 21, 8–13 (2012), special edition
2. J.N. Butterfield: The End of Time?, arXiv:gr-qc/0103055 (2010)
3. FQXI essay competition: http://fqxi.org/community/forum/category/10 (2010)
4. FQXI meeting on time: http://fqxi.org/conference/2011 (2011)
5. S.W. Hawking, G.F.R. Ellis: The Large Scale Structure of Space-Time (Cambridge Univ. Press, Cambridge 1973)