DOI

A DOI, or digital object identifier, is a persistent alphanumeric code assigned to a journal article, book, dataset, or other scholarly object. Unlike an ordinary web address, a DOI is designed never to change: even if the publisher moves the content, the identifier resolves to its current location through a central registry. A DOI usually begins with "10." followed by a publisher prefix and a document suffix.

For a thesis writer, DOIs are the most reliable way to identify and retrieve sources. Many citation styles now require them in reference entries, and citation managers use them to pull accurate metadata automatically. Recording the DOI for every source as you collect it also makes later verification easy: pasting the identifier into a resolver confirms that the reference is real, locatable, and correctly described.