
Zotero is citation manager that allows you to manage research. It collects and organizes different kinds of sources including scholarly articles, websites, and PDFs. It is an open source tool and available online or for download at https://www.zotero.org/.
It includes plugins to automatically import citations from the web and library resources, and it will automatically build your bibliography for you in the citation style of your choice (APA, MLA, Chicago, IEEE, and more).