Unknown "ContentType" in Xpath

[amesga]

publ-a11y/a11y-meta-display-guide/2.0/techniques/onix-metadata/index.html

Line 790 in 459dba6

<li><b>LET</b> <var>non_textual_content_audio</var> be the result of calling <a href="#check-for-node">check for node</a> on <var>onix</var>, <code class="xpath">/ONIXMessage/Product/DescriptiveDetail/DescriptiveDetail[ContentType = "21" or ContentType = "22"] </code>.

There are multiple instances where ContentType is referenced in the Xpath statements, but I don't believe ContentType is a valid term. Should this be PrimaryContentType or ProductContentType? Or both, similar to:

publ-a11y/a11y-meta-display-guide/2.0/techniques/onix-metadata/index.html

Line 506 in 459dba6

<li><b>LET</b> <var>non_textual_content_images</var> be the result of calling <a href="#check-for-node">check for node</a> on <var>onix</var>, <code class="xpath">/ONIXMessage/Product/DescriptiveDetail[PrimaryContentType = "07" or PrimaryContentType = "18" or PrimaryContentType = "19" or PrimaryContentType = "12" or PrimaryContentType = "49" or PrimaryContentType = "20" or ProductContentType = "07" or ProductContentType = "18" or ProductContentType = "19" or ProductContentType = "12" or ProductContentType = "49" or ProductContentType = "20"]</code>.</li>

[rickj]

@gregoriopellegrino @gautierchomel @avneeshsingh just FYI, this is from one of the VitalSource team members.

[chrisONIX]

There are multiple instances where ContentType is referenced in the Xpath statements, but I don't believe ContentType is a valid term.
This is correct - ContentType does not exist on it's own in ONIX
Should this be PrimaryContentType or ProductContentType?
Yes tt should be both