--which mention the ranges (the ones is the McArthur papers are the ones used by most labs in the US):
http://www.ncbi.nlm.nih.gov/pubmed/9865794
http://www.dafml.unito.it/anatomy/pa...pidermiche.pdf
http://www.mendeley.com/research/dis...al-human-skin/
This Aetna policy paper is also good to peruse, mostly as a summary of the work done in the area recently:
http://www.aetna.com/cpb/medical/data/700_799/0774.html