1. Papadias, D., Sellis, T.: A Pictorial Query-by-Example Language. Journal of Visual Languages and Computing 6(1), 53–72 (1995)
2. Lecture Notes in Computer Science;S. Kaushik,1998
3. Calcinelli, D., Mainguenaud, M.: Cigales, a visual language for geographic information system: the user interface. Journal of Visual Languages and Computing 5(2), 113–132 (1994)
4. Meyer, B.: Beyond Icons: Towards New Metaphors for Visual Query Languages for Spatial Information Systems. In: First Intern. Workshop on Interfaces in Database Systems, pp. 113–135. Springer, Heidelberg (1993)
5. Blaser, A.D., Egenhofer, M.J.: A Visual Tool for Querying Geographic Databases. In: Proc. ACM AVI 2000, pp. 211–216. ACM Press, New York (2000)