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2. ‘Classifying inaccessible cardinals’;Hanf;Notices Amer. Math. Soc.,1961
3. S. C. Kleene and R. Vesley, ‘The foundations of intuitionistic mathematics’, Amsterdam (1965)
4. G. Kreisel, ‘Mathematical Logic’, Lectures on modern mathematics, (ed. Saaty), vol. 3(1965), pp. 95–195
5. R. MacDowell and E. Specker, ‘Modelle der Arithmetik’, Infinitistic Methods, Warsaw (1961), pp. 257–263