"Undefined References" in Latex

1. Run LaTeX
2. Run BibTeX
3. Run LaTeX
4. Run LaTeX

So, after every change in your .bib file, you have to run BibTeX again, followed by running LaTeX two times afterward. Of course, if you're using pdflatex (or xelatex), the same applies for it: pdflatex > BibTeX > pdflatex > pdflatex.


source: http://www.latex-community.org/forum/viewtopic.php?f=50&t=9280