I have read the examples here: http://framework.zend.com/manual/en/zend.gdata.spreadsheets.html

But those examples assume the spreadsheet to be read needs authentication:

$service = Zend_Gdata_Spreadsheets::AUTH_SERVICE_NAME;
$client = Zend_Gdata_ClientLogin::getHttpClient($user, $pass, $service);
$spreadsheetService = new Zend_Gdata_Spreadsheets($client);
$feed = $spreadsheetService->getSpreadsheetFeed();

The spreadsheet I am going to read from is a public one, so I don't really need to provide any authentication right? And what I need to provide is just the url of the spreadsheet.

I tried to read the class description here but still have no idea how it can be done: http://framework.zend.com/apidoc/core/Zend_Gdata/Spreadsheets/Zend_Gdata_Spreadsheets.html