Liferay Scheduler

Very good Liferay Scheduler post:
http://itsliferay.blogspot.com/2012/08/implement-scheduler-in-liferay-61.html
https://liferayazam.wordpress.com/2012/06/10/create-a-scheduler-in-liferay-6/
http://pmkathiria.blogspot.com/2013/06/how-to-write-simplecron-scheduler-in.html