Mendeley

Mendeley is a free reference manager and an academic social network. Manage your research, showcase your work, connect and collaborate. To use Mendeley you’ll need to register for the first time. Its free and fast.  

Advantages:-
1. Create and access your library, everywhere – Add papers directly from your browser with a few clicks or import any documents from your desktop. Access your library from anywhere. Windows, Mac, Linux and all browsers.
2. Easy referencing – Generate references, citations and bibliographies in a whole range of journal styles with just a few clicks.
3. Build your Research network – 30 million references and over 6 million researchers to discover. 
Please Visit: [ https://www.mendeley.com/ ] Zotero

Zotero is a free, easy-to-use tool to help you to collect, organize, cite, and share research. Libraries are backed up online allowing sharing between computers and even multiple users. Zotero makes it easy to keep your reference library organised and ‘clean’. Reference libraries are compatible with other reference management programs, and difficulties can be quickly addressed via online forums.
Please visit : [ https://www.zotero.org/ ]