What is a DOI, and how do I find one?
Answer
A Digital Object Identifier, or DOI, is a tag given to each book, article, or chapter that gives it a persisting identifiable alphanumeric code. It makes it poossible to search directly for items based on their DOI alone. It's not mandatory that all publications register DOIs, but most scholarly publishers and some governmental agencies have assigned DOIs to the works they publish. APA citation style requires that the DOI be included in the reference list entries.