1. Michael R. Carey and David S. Johnson, Computers and Intractability, W. H. Freeman and Co., San Francisco, 1979.
2. Min-Yu Hsueh, “Symbolic layout and compaction of integrated circuits,” Memorandum No. UCB/ERL M79/80, University of California, Berkeley.
3. Paul A. Jensen and J. Wesley Barnes, Network Flow Programming, John Wiley and Sons, Inc., New York, 1980.
4. Donald B. Johnson, “Efficient algorithms for shortest paths in sparse networks,” Journal of the Association for Computing Machinery, Vol. 24, No. 1, pp. 1–13, January 1977.
5. Donald B. Johnson, private communication, July 1982.