1. Fisher, H. Various documents on SYIVIAP are obtainable from the Laboratory for Computer Graphics, Harvard University, Cambridge, Mass., U.S.A.
2. This photograph is reproduced by the kind permission of Mr H. O'Brien who developed a system for this during December 1967.
3. Gaits, G. M. A coordinate referencing system for land use planning, Paper 1. General Concepts. Urban Planning Direc-torate, M.H.L.G. (Out of print).
4. D-Mac Ltd, Queen Elizabeth Avenue, Glasgow, S.W. 2.