Hongzhi Song Edwin P. Curran Roy Sterritt Multiple foci visualisation of large hierarchies with FlexTree. 19-35 2004 3 Information Visualization 1 http://www.palgrave-journals.com/cgi-taf/DynaPage.taf?file=/ivs/journal/v3/n1/abs/9500065a.html db/journals/ivs/ivs3.html#SongCS04