This page illustrates how to interpret the parts of an MLA citation for different types of sources. This is important when one has a citation in hand (for example, from the bibliography of a journal article, from a website, or from a professor) and wants to track down the original source.
Although citations look different in other styles such as APA and Turabian, the same information is generally present, but with a different order and formatting.
A DOI, or digital object identifier
What does a doi look like in a citation?