Citationsy is a no-nonsense reference collection and bibliography creation tool for people who value simplicity, privacy, and speed.
Mendeley is a free reference manager and academic social network that can help you organize your research, collaborate with others online, and discover the latest research in your field
ReadCube is a low-cost desktop and browser-based program for managing, annotating, and accessing academic research articles
RefWorks is web-based bibliographic software that enables you to organize your research, include citations while you write your paper, build a bibliography in a variety of formats, import references from many data sources, and create bibliographies in different document formats (Word, RTF, HTML, etc.).
Zotero collects all your research in a single, searchable interface. You can add PDFs, images, audio and video files, snapshots of web pages. Zotero automatically indexes the full-text content of your library, enabling you to find exactly what you're looking for.
Just as it is important to check that the sources you use in your research are peer reviewed, it is also important to cite the sources you use in your own work.
There are numerous citation styles, depending on the field you are working in and on the preferences of your professors. Below are some common citation styles, and links to citation manuals:
Publication Manual of the American Psychological Association by 
MLA Handbook by 
Cite Right, Third Edition by CITATIONS
Citations are the in-text reference that gives brief details (author, date, page) of the source you are quoting or referring to. This citation corresponds with the full details of the work (title, publisher, etc) given in your reference list or bibliography, so that the reader can identify and/or find the source.
REFERENCE LIST
A list of references at the end of your paper that includes the full information for your citations so that the reader can easily identify and retrieve each work (journal articles, books, webpages, etc). Your reference list contains all the items you have cited or directly quoted from.
BIBLIOGRAPHY
A list of works you have consulted for your paper, but not cited in the Reference List. Works should be listed in alphabetical order by author and laid out in the same way as items in your reference list. If you can cite from every work you consulted, you will only need a reference list.
Always check the guidance you are given for your research paper to find out if you are expected to submit work with a reference list and a bibliography.
