Software verification 12th International Conference, VSTTE 2020, and 13th International Workshop, NSV 2020, Los Angeles, CA, USA, July 20-21, 2020 : revised selected papers - Christakis, Maria 1986-; Polikarpova, Nadia 1985-; Duggirala, Parasara Sridhar; Schrammel, Peter (Springer, 2020)