Handling Concurrency for the List

http://blogs.technet.com/b/stefan_gossner/archive/2011/11/10/using-synchronous-quot-after-quot-events-e-g-itemupdated-in-sharepoint-2010.aspx http://sharepoint.stackexchange.com/questions/25542/what-happens-if-an-earlier-event-receiver-throws-an-error https://karinebosch.wordpress.com/walkthroughs/event-receivers-walkthrough2/ http://sppms.blogspot.in/2012/05/sharepoint-2010-event-receivers-and.html http://www.sharepoint-tips.com/2012/01/importance-of-synchronous-event.html