Graph theory and combinatorics, Proc. Conf. Hon. P. Erdős, Cambridge 1983, 259-271 (1984).
[For the entire collection see Zbl 0543.00003.]
A planar permutation of size 2M is defined by two oriented Jordan curves intersecting in the plane in 2M points, one point being the root. When the points are labelled from 1 to 2M in the order in which they occur on one of the curves, beginning at the root, the permutation appears on the other curve. For the sake of solving different problems, each planar permutation of size 2M can be represented by two particular sets of 2M nested parentheses, by a particular kind of plane graph with 2M edges, or by a way of folding a ring of 2M stamps.