Is there an open source tool for producing bibtex entries from paper PDFs? In the desktop application for Mendeley, it's possible to import a PDF and have the bibliographic data automatically extracted (or perhaps looked up, I'm not sure).  This feature is more or less reliable.  However, Mendeley's code is closed source (they once promised to release the source, but then they were bought by Elsevier).  I'm looking for an open source tool that takes one or more PDFs as input and returns a bibtex entry for each.  

I've found the following, but couldn't get either of them to work:


cb2Bib
pdfmeat


At present, the fastest alternative I know is to copy/paste the title into Google Scholar, and click the link to bibtex.  That's very nice, but I'm wondering if there is something more automated.
I use Zotero which in itself is a system for handling references, it comes as both a plugin to Firefox and as standalone. I use the standalone version to extract reference information from pdf and then export to, in my case, BibTeX .bib format. There are possibilities to export to other formats as well.