1. Bounded Queries to SAT and the Boolean Hierarchy;Beigel,1987
2. Relativizations of the P ≟ NP question;Baker;SIAM J. Comput.,1975
3. On isomorphisms and density of NP and other complete sets;Berman;SIAM J. Comput.,1977
4. The Boolean hierarchy: hardware over NP;Cai,1985
5. The Boolean hierarchy: hardware over NP;Cai,1986