 Another way to add an item is by identifier. An identifier is a code or number assigned to published items. For example, a journal article might have a DOI or digital object identifier. A book will have an ISBN. If you know this code or number of a source you want to add to your Zotero library, select the wand-like icon. This is add items by identifier. Enter in the number. Hit enter or return on your keyboard. And this will hopefully produce a new item with its pertinent information in the right-hand window.