Unsatisfiable instances were therefore commonly solved using backtrack search solvers.
David Pereira, Inês Lynce, Steven Prestwich 2009, 'On Improving Local Search for Unsatisfiability', Electronic Proceedings in Theoretical Computer Sciencehttp://arxiv.org/pdf/0910.1244v1. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)