Single Atom <entry> elements are also valid by themselves. Usually the URL for an entry is the feed’s URL
followed by /<entryId>, such as http://atom.example.com/feed/1, using the example URL we used above. This
pattern may exist for some web services which use Atom as a container syntax.
If you read a single entry, you will have a Zend\Feed\Reader\Entry\Atom object.