A. Barr.
  <b>Superquadrics and angle-preserving transformations</b>.
  <i>IEEE Computer Graphics and Applications</i>, 1(1):11-23, 1981.
  <A HREF="http://vis.cs.brown.edu/results/bibtex/Barr-1981-SAP.bib">(bibtex:
  Barr-1981-SAP)</A>.<br />