1. Bayliss BT & Edwards SL (1969) Industrial Demand for Transport. HMSO
2. Cattell RB (1965) Factor analysis: an introduction to essentials. Biometrics 21: 190–215
3. Child D (1970) The Essentials of Factor Analysis. Holt Rinehart and Winston
4. Christoper, Mole, Rushton & Wills (1983) Effective Distribution Management. Pan Books
5. Collins L & Walker DF (Eds) (1975) Locational Dynamics of Manufacturing Activity. Wiley, London