Hi,
don't worry, honest mistake.
The correct way to point to the paper is:
Abbas, S.; Merabti, M.; Llewellyn-Jones, D.; Kifayat, K., "Lightweight Sybil Attack Detection in MANETs," Systems Journal, IEEE , vol.7, no.2, pp.236,248, June 2013
doi: 10.1109/JSYST.2012.2221912
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6363514&isnumber=6504497
And you could mention that, in case of need, you can provide a copy.
This is, basically, the problem of paywalls and paid journals. You can't freely distribute the papers, and you have to either link the publisher's page (but not everybody will be able to access it), or to link to a semi-legal copy.
Semi-legal could be totally legal (the author's copy) or living on the edge (like many "research" websites, also hosting people's papers).
Anyway, I'll try to check the paper and see how hard it would be to do it in ns-3.
Cheers,
T.