  Computability logic is a formal theory of computability. The earlier article
"Introduction to cirquent calculus and abstract resource semantics" by
Japaridze proved soundness and completeness for the basic fragment CL5 of
computability logic. The present article extends that result to the more
expressive cirquent calculus system CL6, which is a conservative extension of
both CL5 and classical propositional logic.
