Alternative to Mendeley

[Jorge Peixoto de Morais Neto]

Hi.  I use Emacs and Auctex.  For my academic research, so far I have made
notes in several files - one for each paper.  Several people have recommended
Mendeley to me.  Mendeley is proprietary (even though it is gratis) and I
prefer open source.  I only tolerate proprietary software if it is much better
than the open alternative.  Can you recommend a good alternative to Mendeley?
Integration with Emacs is a plus but not mandatory.  But it must be something
I can learn (the basics) in an afternoon.

Regards

--
The sooner we fight global heating the lesser the cost.