Another useful way to keep track of your sources and citations is to use a citation manager. There are many citation managers, both free and for purchase, but a good citation manager is one that is easy for you use and compatible with the style that you are writing in.
Zotero is an open access (free) citation manager that can be used as a desktop download, as an app on your device, in your browser, or as a browser extension. Zotero works in hundreds of citation styles and can keep track of many different formats and types of sources. Feel free to ask me about Zotero!