(3) owes much to the joint work of Blok and Pigozzi exploring the different forms that the well-known deduction theorem of classical propositional calculus and first-order logic takes on in a wide variety of logical systems.
(3) is indebted to the collaborative efforts of Blok and Pigozzi in examining various forms that the well-known deduction theorem of classical propositional calculus and first-order logic takes on within a diverse range of logical systems.