@article {hall_estimating_2002, title = {Estimating and depicting the structure of a distribution of random functions}, journal = {Biometrika}, volume = {89}, number = {1}, year = {2002}, pages = {145{\textendash}158}, url = {http://biomet.oxfordjournals.org/content/89/1/145.short}, author = {Hall, Peter and Heckman, Nancy E.} }