...X¹¹

This work was supported by a Natural Sciences and Engineering Research Council of Canada Grant A-5692 and a Deutsche Forschungsgemeinschaft Grant Sto167/1-1. It was started during the first author's stay with the Data Structuring Group in Waterloo.

...├╝ggemann-Klein²²

Institut f├╝r Informatik, Universit├ñt Freiburg, Rheinstr. 10–12, 7800 Freiburg, West Germany

... Wood³³

Data Structuring Group, Department of Computer Science, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada

... dimensions⁴⁴

The term dimension is used in TEX to describe physical measurements of typographical objects, like the length of a word.

... nodes⁵⁵

The height h and the number of nodes N refer to the drawing of the tree. N is the number of circles, squares etc. actually drawn, and h is the number of levels in the drawing minus 1.