@article{upgma-ipl,
 author = {Ilan Gronau and Shlomo Moran},
 title = {{Optimal implementations of UPGMA and other common clustering algorithms}},
 journal = {Inf. Process. Lett.},
 volume = {104},
 number = {6},
 year = {2007},
 issn = {0020-0190},
 pages = {205--210},
 doi = {http://dx.doi.org/10.1016/j.ipl.2007.07.002},
 publisher = {Elsevier North-Holland, Inc.},
 address = {Amsterdam, The Netherlands, The Netherlands},
 }