1. Brogden, Hubert E. An approach to the problem of differential prediction.Psychometrika, 1946,11, 139–154.
2. Cowles Commission Monograph;George B. Dantzig,1951
3. Dantzig, George B. Application of the simplex method to a transportation problem. Chapter XXIII of the monograph of (2).
4. Dwyer, P. S. Basic theory and methods in optimal classification of personnel. Personnel Research Branch, Department of the Army, 1953.
5. Lord, Frederick M. Notes on a problem of multiple classification.Psychometrika, 1952,17, 297–304.