Theory and applications of satisfiability testing -- SAT 2018 : 21st International Conference, SAT 2018, held as part of the Federated Logic Conference, FloC 2018, Oxford, UK, July 9-12, 2018, Proceedings /: 21st International Conference, SAT 2018, held as part of the Federated Logic Conference, FloC 2018, Oxford, UK, July 9-12, 2018, Proceedings. (2018)