1. I use some abbreviations which are not standard or self-explanatory, namely.
2. HB for “Handbook of Mathematical Logic,” J. Barwise, ed., North-Holland, Amsterdam, 1977.
3. IPT for “Intuitionism and Proof Theory. Proceedings of the Summer Conference at Buffalo, N.Y., 1968,” A. Kino, J. Myhill and R. E. Vesley, eds., North-Holland, Amsterdam, 1970.
4. LNM for Lecture Notes in Mathematics, Springer, Berlin.
5. Bernays, P., 1922, Über Hilberts Gedanken zur Grundlegung der Arithmetik, Jahresbericht DMV, 31:10–19.