1. N. N. Vorob'ev,Constructive propositional calculus with strong negation (in Russian),Doklady Akademii Nauk SSSR, 85 (1952), pp. 456–468.
2. N. N. Vorob'ev,The problem of provability in constructive propositional calculus with strong negation. (in Russian),ibid., pp. 689–692.
3. N. N., Vorob'ev,Constructive propositional calculus with strong negation (in Russian),Transactions of Steklov's Institute 72 (1964), pp. 195–227.
4. A. A. Markov,Constructive logic (in Russian),Uspekhi Matematičeskih Nauk 5 (1950), pp. 187–188.
5. A. Białynicki-Birula andH. Rasiowa,On the representation of quasi-Boolean algebras,Bulletin de l'Académie Polonaise des Sciences 5 (1957), pp. 259–261.