Quote From TreeofLife:
the van, von and der should be lower case and should be ignored for alphabetical listing in a bibliography.
I'm not sure about surnames deviating from the usual English letters; I would just put Sørensen after the other surname beginning with SO.
Thanks mate, but I am even more confused now. Harvard system says one lists these surnames under V, V, D. If you search on google for 'harvard system van von der'; the pdf on the first result. No idea what is right and what is wrong any more.