European Meeting of the Association for Symbolic Logic, Kiel, Federal Republic of Germany, 1974. - G. H. Muller; Arnold Oberschelp; K. Potthoff (J. Symb. Log., 1976)

A simple tree lemma and its application to a counterexample of Philips. - Klaus Potthoff (Arch. Math. Log., 1977)

Orderings of Types of Countable Arithmetic. - K. Potthoff (Math. Log. Q., 1978)