Byzantine consensus in asynchronous message-passing systems: a survey

Hi, I saw recently the post from Hive account@heiditravels about Hashgraphs and Swirlds (https://steemit.com/cryptocurrency/@heiditravels/more-than-blockchains-how-hashgraph-and-dags-are-different).
I was curious about it, I had a look to the whitepaper on Hashgraphs: I dig a bit further in the references of this paper.

I found this interesting survey about asynchronous consensus written by Miguel Correia, Giuliana Santos Veronese,
Nuno Ferreira Neves and Paulo Verissim.
Follows the link down below:
http://www.di.fc.ul.pt/~nuno/PAPERS/IJCCBS11.pdf

I think it is pretty interesting because the survey presents several asynchronous techniques that was used to check the boundaries of the determinism of the synchronous consensus.

The survey is short, easy to read and not too technical.

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