1. W. A. Woods, R. M. Kaplan, and B. N. Webber, "The lunar sciences natural language information system," Final Report, vol. BBN Report 2378, Bolt Beranek and Newman Inc., Cambridge, Massachusetts, 1972.
2. Androutsopoulos, G.D. Ritchie, P. Thanisch 1995, "Natural Language Interfaces to Databases-An Introduction" In Natural Language Engineering, Vol 1, part 1, pp.29--81, 1995.
3. Rodolfo A. Pazos Rangel, Joaquín Perez O., Juan Javier Gonzalez B., Alexander Gelbukh, Grigori Sidorov, and Myriam J. Rodriguez M., "A Domain Independent Natural Language Interface to Database Capable of Processing Complex Queries", MICAI 2005, Springer, pp. 833--842.
4. Rajeh Khamis, S. Shatnawi, "Toward Enhanced Natural Language Processing to Databases: Building a Specific Domain Ontology Derived from Database Conceptual Model" 7th International Conference on Informatics and Systems, IEEE, March 2010.
5. Mizoguchi R. 2004. Tutorial on Ontological engineering: part 3: Advanced course of ontological engineering. New Gen. Comput. 22, 2 (Jan. 2004), pp.198--220.