Robust estimation of regression parameters with heteroscedastic errors in the presence of outliers (presented at the 8th WSEAS international conference on applied computer and computational science, Hangzhou China, 20-22 May 2009) - Midi, Habshah; Rana, Sohel; Imon, A. H. M. Rahmatullah (Faculty of Science, Universiti Putra Malaysia, 2009)