There are two kinds of case studies from Harvard, so it depends.
Yes, you may link the case studies if they are in EBSCO.
There are two kinds of cases, the HBR Case Study ones are in Harvard Business Review itself and in EBSCO, like this one:
However, there are also Harvard Business School Case Studies - which we can only provide individually if requested through Document Express, and cannot be assigned in courses (i.e. they can't instruct each student to request it individually). If the school wanted to assign one of these they would need to license it from HBSP.