See probabilistically checkable proofs for more details. Another interactive proof system characterizing NEXPTIME is a certain class of probabilistically checkable proofs. Locally testable codes have a lot in common with probabilistically checkable proofs (PCPs). His two most-cited papers are on multi-prover interactive proofs and on probabilistically checkable proofs. In a probabilistically checkable proof system, a proof is represented as a sequence of bits. It includes currency held by the nonbank public and checkable deposits. Also, NOW (or negotiable orders of withdrawal) accounts allowed checkable deposits to earn interest. Many examples of problems with checkable algorithms come from graph theory. That is, the membership test is checkable for "I", provided a characteristic set of "I".