"Logique mathématique." . . "Logic." . . "Modalité (logique)" . . "Modalité (logique)." . "Modalité (Logique)" . "déduction." . . "Bewijstheorie." . . "Deduktion." . . "Folgerung." . . "Déduction (Logique)" . . "Modallogik." . . "Metamathematics." . . "déduction naturelle (calcul logique) preuve - théorie." . . "Modality (Logic)" . . "Logica." . . "Lógica." . "Logic, Symbolic and mathematical." . . "Lógica simbólica y matemática." . . "Deductie." . . "Logica matematica." . . "Lògica matemàtica." . "Logika." . . "Modalność (logika)." . . "Natural deduction : A proof-theoretical study" . . . . . . . . . . "Natural deduction - a proof-theoretical study" . . . . . . . . . . . . . . . . . "Natural Deduction. A proof-theoretical study"@en . . . . "Natural deduction : a proof-theoretical study"@en . "Natural deduction : a proof-theoretical study" . . . . . . "Natural Deduction; A Proof-Theoretical Study"@en . . . . . . . . . . . "Natural deduction; a proof-theoretical study" . . "NATURAL DEDUCTION : A Proof-Theoretical Study"@it . . "Natural deduction a proof-theoretical study" . "Natural deduction a proof-theoretical study"@en . . . . . . . . . . "Natural deduction" . . . . . . . . . . . . . . "Logique symbolique et mathématique." . . . . "Logik." . . "Logika symboliczna i matematyczna." . . "Modalità (Logica)" . . "Gentzen, Gerhard." . . "Mathematische Logik." . . "logique." . . "Logique." . "Metamatemática." . .