If you are in a class or any of the following subjects are your major, you should probably use APA format:
The most recent edition of this book is in the reference area on the 2nd floor of the library. While you can't check out reference items, you may be able to check out older editions of the book at the same call number on the 3rd floor.
DOI stands for Digital Object Identifier. It is a persistent, unique number that identifies a piece of online or digital information, such as a journal article, a chapter in an online book, a data set, a map, and so on. Students most often encounter DOIs when they're citing journal articles. Keep in mind that not every journal article will have a DOI assigned to it! Look for the DOI on the first page of the article, either at the top or bottom. You need to include them in your citation as they are very helpful when trying to locate the article later.