Not specific to the islands issue, but here's a good (and completely unclass) refresher on the PLA(N) for your reading pleasure. It does give some background on why those claims are being made.
http://www.oni.navy.mil/Intelligence_Community/china_media/2015_PLA_NAVY_PUB_Interactive.pdf
http://www.oni.navy.mil/Intelligence_Community/china_media/2015_PLA_NAVY_PUB_Interactive.pdf