: this button allows you to create manually new references, if you can not find the reference online.
Save the PDFs you would like to put into your library on your computer, then drag and drop them into your Zotero library. Zotero will automatically attempt to retrieve metadata (title, author, journal...) from the PDF. The PDF is also renamed according to parent metadata.
Zotero uses "translators" to convert the data from library catalogues, databases, or other Web sites such as Google or Amazon. When you are viewing a Web site, if a translator is available, a little icon appears in the URL bar. Just click on it, and the reference is downloaded.
There are different icons, for each kind of documents: blue for books 
, white for journal articles 
... If there are several references on one Web page, the folder icon 
appears, and if you click on it, you can select which references you wish to download.
There are Zotero translators for:
: this button allows you to add references using the ISBN (International Standard Book Number) or the DOI (Digital Object Identifier). All books which are being published nowadays have an ISBN. The DOI is an identifier for electronic documents such as Web pages, or articles published in electronic journals, but most Web pages do not have DOIs. But you can find DOIs in some bibliographic databases.
A new functionality in Zotero 5.0 allows the use of RSS or ATOM feeds to add directly the references of interesting documents to a Zotero library.
Click on the 
button, select "New Feed" and enter the URL or the OPML. The reference can then be added directly into a Zotero library, by clicking on the button "Add to my Library" or by selecting first a specific collection.
