What are some alternatives?
When comparing Qiqqa and Paperpile, you can also consider the following products
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
Docear - Docear
JabRef - Graphical Java application for managing bibtex (. bib) databases.JabRef · JabRef Help · JabRef | Blog · OpenOffice/LibreOffice .
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
Thomson Reuters - The intelligence, technology and human expertise you need to find trusted answers. Thomson Reuters is The Answer Company.
Papers - Papers is a research management software designed to streamline searching, aggregating and citing digital reference materials.