1st December 2006: Change to arXiv identifiers
The arXiv is changing its identifier policy. From 1st January 2007 all preprints will have an identifier 0701.0001 instead of hep-th/0701001. This is being done to increase the available identifiers for each month to 9999. The removal of the category from the identifier, such as hep-th, will also make multiple classification easier.