The notion of treewidth of a graph was introduced by {\it N. Robertson} and {\it P. Seymour} [J. Algorithms 7, 309-322 (1986; Zbl 0611.05017)]. For classes of planar graphs (k-outerplanar graphs, graphs with radius k) upper bounds are proved on the treewidth of these graphs. This research is motivated by the fact that many NP-hard graph problems are polynomially solvable when restricted to graphs with bounded treewidth.
R.Klette