4. DOWNS, G. M., BARNARD, J. M. <em>Hierarchical and non-Hierarchical Clustering.</em><ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.daylight.com/meetings/mug96/barnard/E-MUG95.html">http://www.daylight.com/meetings/mug96/barnard/E-MUG95.html</ext-link>
5. IRENE, M. M. <em>Clustering Methods and Algorithms.</em><ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.cse.iitb.ac.in/dbms/Data/Courses/CS632/1999/clustering/dbms.html">http://www.cse.iitb.ac.in/dbms/Data/Courses/CS632/1999/clustering/dbms.html</ext-link>