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2. Najah, M., Pictorial Interfaces to Data Bases, Ph. D. Thesis, Teesside Polytechnic, County Cleveland, UK (1986)
3. Boyle, T.M., The Use of Paper-based Pictorial Interfaces within a. Multi-media Workstation, M. Sc. Thesis, Teesside Polytechnic, County Cleveland, UK (1986)
4. IBM makes usability as important as functionality;Shackel;The Computer Journal,1986
5. Author Languages for CAL;Barker,1987