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@Article{Friendly06hesoft,
author = {Michael Friendly},
title = {Data Ellipses, HE Plots and Reduced-Rank Displays for Multivariate Linear
Models: SAS Software and Examples},
journal = {Journal of Statistical Software},
year = {2006},
volume = {17},
number = {6},
pages = {1–42},
url = {http://datavis.ca/papers/hesoft.pdf},
}