I couldn't find anything definitive, but here are some papers on the topic: http://mint.typepad.com/mypapers/pp017-lizorkin.pdf http://mint.typepad.com/mypaper

I couldn't find anything definitive, but here are some papers on the topic: http://mint.typepad.com/mypapers/pp017-lizorkin.pdf http://mint.typepad.com/mypapers/pp017-lizorkin.pdf http://www.fran.it/articles/wikimania_bellomi_bonato.pdf http://www.fran.it/articles/wikimania_bellomi_bonato.pdf http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=arnumber=4559785 http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=arnumber=4...