[etc-hosts]

This article explains a theory of how yupana worked

http://www.mathematicsmagazine.com/Articles/Yupana.php

[dang]

Thanks! we've changed the link to that from https://cacm.acm.org/blogcacm/technical-marvels-part-3-the-y... above.

[kallistisoft]

Thank you for posting an article worth reading :)