Answer Last Updated: Aug 05, 2016 Views: 59
The AMA Manual of Style states in Chapter 3.15.1 Online Journals:
When the DOI is provided, it is preferable to cite it rather than the URL.
Note: The DOI is provided immediately after ‘‘doi:’’ and is set closed up to it, per convention. No accessed date is required for the DOI, making it the last item in the reference.