Course
Structured Data - Change History & Alerts

Google modified their documentation to clarify that you must mark up at least three courses to be eligible for the Course rich result;

• The courses can be on separate detail pages, or in an all-in-one page.
• You must add Carousel markup to either a summary page or an all-in-one page (and they now provide an example for each of these).

This is not a new requirement; it was previously only documented in the Carousel documentation.