https://developer.paypal.com/webapps/developer/docs/classic/ipn/integration-guide/IPNIntro/
Обсуждение на форуме http://www.etown.ru/s/topic/1740-%D0%BD%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%B9%D0%BA%D0%B8-%D0%BF%D0%BB%D0%B0%D1%82%D0%B5%D0%B6%D0%BD%D0%BE%D0%B9-%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D1%8B-paypal/?hl=paypal
