|| G. Salton, A. Wong and C. Yang, ′A vector space model for automatic indexing′, Commun. ACM, vol. 18, no. 11, pp. 613-620, 1975.|
 G. Salton and C. Buckley, ′Term-weighting approaches in automatic text retrieval′, Information Processing & Management, vol. 24, no. 5, pp. 513-523, 1988.
 J. Wu, ′Applying relevance feedback to construct a vector space model with concepts as the dimension value′, National Central University, Taiwan, 2013.
 M. Sahlgren and R. Cöster, ′Using Bag-of-Concepts to Improve the Performance of Support Vector Machines in Text Categorization′, in Proceedings of the 20th international conference on Computational Linguistics, Geneva, Switzerland, August 23-27, 2004, p. 487.
 A. Alahmadi, A. Joorabchi and A. E. Mahdi, ′A New Text Representation Scheme Combining Bag-of-Words and Bag-of-Concepts Approaches for Automatic Text Classification′, in GCC Conference and Exhibition (GCC), 2013 7th IEEE, Doha, November 17-20, 2013, pp. 108-113.
 G. Salton and M. McGill, Introduction to modern information retrieval. New York: McGraw-Hill, 1983, pp. 117-122.
 G. Salton, The SMART Retrieval System—Experiments in Automatic Document Processing. NJ, USA: Prentice-Hall, 1971.
 L. Cai and T. Hofmann, ′Text Categorization by Boosting Automatically Extracted Concepts′, in Proceedings of the 26th annual international ACM SIGIR conference on Research and development in information retrieval, Toronto, Canada, July 28-August 1, 2003, pp. 182-189.
 G. Evgeniy and S. Markovitch, ′Overcoming the Brittleness Bottleneck Using Wikipedia: Enhancing Text Categorization with Encyclopedic Knowledge′, in proceedings of the 21st national conference on Artificial intelligence - Volume 2, Boston, USA, July 16-20, 2006, pp. 1301-1306.
 N. N. Myat and K. H. S. Hla, ′A combined approach of formal concept analysis and text mining for concept based document clustering′, in Proceedings of the 2005 IEEE/WIC/ACM international conference on Web Intelligence, Compiegne University of Technology, France, September 19-22, 2005, pp. 330-333.
 P. G. Anick and S. Tipirneni, ′The paraphrase search assistant: terminological feedback for iterative information seeking′, in Proceedings of the 22nd annual international ACM SIGIR conference on Research and development in information retrieval, California, USA, August 15-19, 1999, pp. 153-159.
 C. C. Su, ′Document clustering based on vector space model with concepts as the dimension value′, National Central University, Taiwan, 2007.
 F. Crestani and S. Wu, ′Testing the cluster hypothesis in distributed information retrieval′, Information Processing & Management, vol. 42, no. 5, pp. 1137-1150, 2006.
 D. Lawrie, W. Bruce Croft and A. Rosenberg, ′Finding topic words for hierarchical summarization′, in Proceedings of the 24th annual international ACM SIGIR conference on Research and development in information retrieval, New Orleans, USA, September 9-12, 2001, pp. 349-357.
 F. Sebastiani, ′Machine learning in automated text categorization′, CSUR, vol. 34, no. 1, pp. 1-47, 2002.
 C. Chang and C. Lin, ′LIBSVM′, ACM Transactions on Intelligent Systems and Technology, vol. 2, no. 3, pp. 1-27, 2011.
 E. Voorhees and D. Harman, ′Overview of the Sixth Text REtrieval Conference (TREC-6)′, Information Processing & Management, vol. 36, no. 1, pp. 3-35, 2000.
 X. Hu, X. Zhang, C. Lu, E. K. Park and X. Zhou, ′Exploiting Wikipedia as external knowledge for document clustering′, in Proceedings of the 15th ACM SIGKDD international conference on Knowledge discovery and data mining, Paris, France, June 28-July 1, 2009, pp. 389-396.
 D. Harman, ′Relevance feedback revisited′, in Proceedings of the 15th annual international ACM SIGIR conference on Research and development in information retrieval, Copenhagen, Denmark, June 21-24, 1992, pp. 1-10.
 I. RUTHVEN and M. LALMAS, ′A survey on the use of relevance feedback for information access systems′, Knowl. Eng. Rev., vol. 18, no. 2, pp. 95-145, 2003.
 S. Robertson and K. Jones, ′Relevance weighting of search terms′, J. Am. Soc. Inf. Sci., vol. 27, no. 3, pp. 129-146, 1976.