A citation manager helps us to keep track of articles and books as we refer to them during any Literature Review, create references, citations and bibliographies in Microsoft Word. Using any citation manager is more than a big help to most research scholars. Each manager also has built-in connections to Google and MS Word.

For a comparative chart between some of the popular Reference Management tools, please check the following websites :

https://www.library.wisc.edu/services/citation-managers/comparison-chart/

http://guides.library.upenn.edu/citationmgmt

Tools :

   BibDesk : "BibDesk is a graphical bibliography manager for OS X, providing powerful BibTeX file management for Mac users." (Free, Mac)
   BibMe : online bibliography-maker generating MLA, APA, Chicago and Turabian citations (Free, web-based)
  Bibus : open source "bibliographic and reference management software" that is designed for collaboration, hierarchical organization of resources, and live query of medical databases, such as PubMed (Free, cross-platform)
  Bookends: reference manager with support for retrieving bibliographic information and related files from the Web, automatically generating bibliographies, etc. (Commerical, Mac)
   Citeline: "a service to facilitate the web publishing of bibliographies and citation collections as interactive exhibits and facilitate the sharing of this type of data." Can import Zotero and BibTex files. Part of MIT's Simile project. (Free, web-based)
   CiteUlink: "A free service for managing and discovering scholarly references...[used] to organise your academic papers." (Free, web-based)
   Connotea [Review]:"Free online reference management for all researchers, clinicians and scientists" (Free, web-based)
  EndNote: "Web-based tool for managing and citing references in papers and creating bibliographies...integrates the following tasks into one program: Search bibliographic databases on the Internet; organize references, images, PDFs and other files; construct your paper with built-in manuscript templates; watch the bibliography and figure list appear as you write" (Commercial, web-based)
   Heurist: a collaborative academic bookmarking, bibliographic, and general database with rich data types, annotation, record interlinking and publication capabilities, including bibliography output and citation within Word. Reference import and bookmarklet. (Free, web-based; open source planned 2009)
   JabRef: "bibliography reference manager" that generates BibTeX files (Open source, cross-platform)
   Mendeley: "Free social software for managing and sharing research papers. It is also a Web 2.0 site for discovering research trends and connecting to like-minded academics." (Free, Windows/Mac/Linux)
   NoodleTools: MLA, APA, Chicago, and Turabian integrated citing and note-taking teaching software which prompts for analysis of source types and is unique in offering personal help on any citation. Instructor/librarian view allows teacher to comment on work-in-progress providing just-in-time feedback in-context (Free and Subscription, web-based)
   OttoBib: allows you to enter an ISBN number and receive a formatted citation (Free, web-based)
  OWL at Purdue: a reference site, maintained by Purdue, which provides the user with many of the style guidelines listed in the handbook of the Modern Language association (Free, web-based)
   Qiqqa: Manage, annotate and tag PDFs; sync collections (Free, PC)
   Referencer: "a Gnome application to organise documents or references, and ultimately generate a BibTeX bibliography file" (Open source, Linux)
   RefWorks [Review]: "RefWorks -- an online research management, writing and collaboration tool -- is designed to help researchers easily gather, manage, store and share all types of information, as well as generate citations and bibliographies." (Commercial, web-based)
  Zotero [Review]: "web-based extension to help you collect, manage, and cite your research sources", compiles a library that can be accessed remotely (Free; Windows/Mac/Linux, requires Firefox browser) 1

References Used for Online Citation Management Tools:

1) https://digitalresearchtools.pbworks.com/w/page/17801648/Citation%20Management%20Tools

2) Comparison Chart available at: https://www.library.wisc.edu/services/citation-managers/comparison-chart/

3) Comparison Chart available at: http://guides.library.upenn.edu/citationmgmt