I´ve been using Zotero for a long time now and I can’t recommend it enough. Along with several plugins, such as ZotFile [1] and ZoteroBetterBibTex [2] I’ve been able to build a very flexible workflow that allows me to work either in a traditional processor, in Latex and even in Markdown+pandoc on iOS. Recently they also added support for Google Docs [3] and it does seems to be working quite well. It enjoys the benefits of open software, such as an engaging community and support.

[1] http://zotfile.com [2] https://retorque.re/zotero-better-bibtex/ [3] https://www.zotero.org/support/google_docs