Pereira, Luiz Carlos, Hausler, Edward Hermann and Paiva, Valeria de, eds. 2004. Advances in Natural Deduction. A Celebration of Dag Prawitz’s Work. Trends in Logic n. 39–54. Dordrecht: Springer.
Veloso, Paulo A. S., Pereira, Luiz Carlos and Hausler, Edward Hermann. 2012. “On What There Must Be: Existence in Logic and Some Related Riddles.”Disputatio 4(34): 879–910.