1. See the lecture notes and references of the other lectures of this summer-school in particular those in J.H. Lowenstein and E. Speer.
2. See for example the Proceedings of the 17thConference in High Energy Physics, London 1974.
3. The derivation of the Gell-Mann Low formula on a formal level can be found in most textbooks on quantum field theory i>e. the formal aspects have been reviewed by S. Gasiorowisz, “Elementary particle Theory”. John Wiley and Sons, Inc. New York 1966.
4. Functional techniques go back to Feynman’s work and have been extensively used for example in papers of Fadejev and collaborators. See also J. Zinn Justin in Lecture Notes in Physics, page 2, Vol. 37, 1975 Springer Verlag.
5. This statement is the prototype of equivalence theorems conneting old fashioned R.P.T. with the modern method of Bogoliubov-Parasiuk-Hepp-Zimmermann and derivates thereof1). It has been called “Folk Theorem” in Wightman’s orientation lecture. The proof of such theorem can probably be found in some forthcoming University of Maryland lecture notes of P.K. Mitter.