pnas2011.bst

PNAS bibtex style updated to match the current fashion in reference layout as of 4 September 2011. Requirements (incomplete, unfortunately) can be found at http://www.pnas.org/site/misc/iforc.shtml#order .

Changes:
- Abbreviate first names as ABC instead of A. B. C.
- Fix: Comma-separate when there are exactly 2 authors
- Use comma instead of & before last author
- Short to first author et al. if > 5 authors
- Dont print volume in bold
- Separate volume and page with colon
- Dont use . between authors and year

Known bugs:
 - First-names with hyphens, say Aaaa-Bbbb incorrectly end up as AB instead of A-B