In light of the title and date of this lecture it is natural to think that it presented the hierarchy of higher types, what is also sometimes called the logical framework of Martin-Löf type theory. A good published reference for this is the chapter by Nordström, Petersson, and Smith in vol 5 of the Handbook of Logic in Computer Science. For the treatment of Pi, which here allows for an induction principle, see also chapter 7 of the book by the same authors and Garner's paper "On the strength of dependent products in the type theory of Martin-Löf".