For use with University of Colorado Boulder digital collections URLs, accessed from the landing page: https://cudl.colorado.edu/luna
Variable 1 is the ARK identifier of the scan. The ARK identifier can be obtained from the full ARK URL, which has the format https://ark.colorado.edu/ark:/ARK identifier. This ARK URL is found in "Identifier ARK" field of the "Media Information" pane on the web page for the scan in question. In some cases, the ARK link might not resolve correctly; this appears to happen when there are multiple linked scans in the library's database.
