1.http://snippets.symfony-project.org/snippets/tagged/criteria/order_by/date

2.Propel API: http://api.propelorm.org/

3.Criteria API: http://www.tig12.net/downloads/apidocs/symfony/lib/plugins/sfPropelPlugin/lib/vendor/propel/util/Criteria.class.html

4.Propel Criteria builder: http://propel.jondh.me.uk/

5.Propel : http://stereointeractive.com/blog/2007/06/12/propel-queries-using-custom-sql-peer-classes-and-criterion-objects/