Matt Kaufmann and J Strother Moore.
Enhancements to ACL2 in Versions 5.0, 6.0, and 6.1.
In: Proceedings of ACL2 Workshop 2013, Ruben Gamboa and Jared Davis, editors.
Electronic Proceedings in Theoretical Computer Science, Volume 114, pp. 5-12. DOI 10.4204/EPTCS.114.1.
The talk was in the following two parts, with links below for each.