Boston University has a list of open business case study repositories. All are free and some are editable.
The Case Centre offers a large and diverse collection of management cases for purchase.
Darden School of Business at the University of Virginia has searchable collection of case studies online. Abstracts and video previews are available but you must purchase any studies that you want. Verified faculty have free access to all content on the site.
Santa Clara University's Markkula Center for Applied Ethics provides free access to cases about technology ethics, including many cases about AI.
Stanford case studies are searchable online. Many of these are available for purchase through Harvard Business School Publishing.
You can find cases on the tech sector using IDC. To search for case studies, enter "case study" in the search box on the main page. You can then use the filters on the left side of the search results page to narrow down the case studies based on audience (tech supplier or tech buyer), document type, topic or region. 
The Financial Times has recently started publishing case studies, many of which concern sustainability. You can find these here or by searching for "business case":
The latest UK and international business, finance, economic and political news, commentary and analysis from the Financial Times.
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Search the following databases to find articles dealing with your particular topic (e.g., employee empowerment and airlines). You can search specifically for case studies in some databases. From the advanced search in both ABI/Inform and Business Source Premier, you can select "case study" under document type.
