1. How to draw a planar graph on a grid;de Fraysseix;Combinatorica,1990
2. Balanced aspect ratio trees and their use for drawing very large graphs;Duncan,1998
3. Planarity-preserving clustering and embedding for large planar graphs;Duncan,1999
4. Multilevel visualization of clustered graphs;Eades,1996
5. Straight-line drawing algorithms for hierarchical graphs and clustered graphs;Eades,1996