References
Georg Kreisel
Second thoughts around some of Gödel's writings
1998
Synthese 114/1
Wolfgang Stegmüller und Matthias Varga von Kibed: Strukturtypen der Logik
1985
Grazer Philosophische Studien 24
The motto of "philosophical investigations" and the philosophy of proofs and rules
1978
Grazer Philosophische Studien 6