the CX-311-085 is the SCWCD6 (JEE6) exam and the CX-310-083 is the SCWCD5 (JEE1.4) exam.
Head First prepares you for the SCWCD5 exam but is a good basis for the SCWCD6 exam. Although you need to prepare for the new EE6 features by reading the specs. As far as I know there are no SCWCD6 specific books yet.
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