 The use of generalized matrices and abstract logics as models for logic systems has proved very useful for the study of selfextensional logics in general and more in particular for the study of the selfextensional logics that are not protoalgebraic such as the logics discussed in  Section 12.  In particular, they have proved very useful for the study of the class of finitary selfextensional logics with a conjunction and the class of finitary selfextensional logics with the deduction-detachment property for a single term, say \(p \rightarrow q\); the logics in this last class are nevertheless protoalgebraic. A logic \(\bL\) has a conjunction if there is a formula in two variables \(\phi(p, q)\) such that