Paper: Inhibition of 5 alpha-reductase activity in human skin by zinc and azelaic acid (1988)

An old paper from 1988 reporting that zinc can be a potent inhibitor of 5-AR.

Inhibition of 5 alpha-reductase activity in human skin by zinc and azelaic acid
https://www.ncbi.nlm.nih.gov/pubmed/3207614