Congratulations, Nasir if you are new to EJB go for EJB3 in action, I read both (EJB3 in action and O'reilly book) and O'reilly's is a bit not aesy to follow I think O'reilly's start making sense after reading EJB3 in action.
The EJB 3 spec can be found -not too surprisingly, really- under the link described as "Ejb 3.0 Spec" above. It points to the spec, the javadocs and the class files.