Allows you to organize and annotate PDFs, insert bibliographies and citations into your research paper and collaborate in groups. Free with an option to upgrade for more storage space.
How to cite sources
A citation is a way of giving credit to individuals for their creative and intellectual works that you utilized to support your research. It can also be used to locate particular sources and combat plagiarism. Typically, a citation can include the author's name, date, location of the publishing company, journal title, or DOI (Digital Object Identifer).