Some alternatives. Permacoin(<a href="http:&#x2F;&#x2F;cs.umd.edu&#x2F;~amiller&#x2F;permacoin.pdf" rel="nofollow">http:&#x2F;&#x2F;cs.umd.edu&#x2F;~amiller&#x2F;permacoin.pdf</a>) has mostly the same security properties, but effectiveily non-outsorceable, and work done is useful. We made the first open-source implementation of that <a href="https:&#x2F;&#x2F;github.com&#x2F;ScorexProject&#x2F;Scorex-Lagonaki&#x2F;tree&#x2F;master&#x2F;scorex-perma" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;ScorexProject&#x2F;Scorex-Lagonaki&#x2F;tree&#x2F;master...</a> .<p>I also have paper draft about better Proof-of-Stake protocol, and would like to share it with people from academias to get a feedback. Please write me ( kushti at protonmail dot ch ). I also have half-written paper draft about PoW+PoS hybrid chain.