Topological Sorting of Large Networks Topological Sorting is a procedure required for many problems involving analysis of networks. An example of one such problem is PERT. The present paper presents a very general method for obtaining topological order. It permits treatment of larger networks than can be handled on present procedures and achieves this with greater efficiency. Although the procedure can be adapted to any machine, it is discussed in terms of the 7090. A PERT network of 30,000 activities can be ordered in less than one hour of machine time. The method was developed as a byproduct of procedures needed by Westinghouse, Baltimore. It has not been programmed and at present there are no plans to implement it. In regard to the techniques described, Westinghouse's present and anticipated needs are completely served by the Lockheed program, which is in current use. CACM November, 1962 Kahn, A. B. CA621120 JB March 17, 1978 5:58 PM 1050 4 441 1226 4 441 441 4 441 758 4 441 1723 5 441 367 5 441 441 5 441 441 5 441 441 5 441 758 5 441 367 6 441 441 6 441 441 6 441