To my non expert eye it appears that the Sybil resistance and hence the entire novelty of the paper is rests on this currently inaccessible citation.

Citations 14 and 15 also seem to be unpublished, and are all by the same authors.

Seems like important sections of this paper were not ready in time for them to perform their ICO.

Yes, citations 5, 14, 15 will be published latter. There is a possibility that some of them will be published next week.

It's coming shortly (days), it's a WIP that needs significant polish, but the core result is there.