This is a report on the papers:
Peter Kirschenhofer and Helmut Prodinger, On the average hyperoscillations of planted plane trees, Combinatorica 2 (1982), 177-186.
Peter Kirschenhofer, On the average shape of simply generated families of trees, J. Graph Theory 7 (1983), 311-32.
Peter Kirschenhofer, Some new results on the average height of binary trees Ars Combin. 16 (1983), A, 255-260.