Search Franklin: Catalog (change the dropdown to Subjects) for terms like: Investments -- Environmental aspects, Investments--Social aspects, Investments -- Moral and ethical aspects, Capitalism -- Moral and ethical aspects, Social Entrepreneurship, Social responsibility of business.
Below are links to some of the e-books available to the UPenn community on the subject of Impact Investing.
You can also access the UPenn subscription to the Stanford Social Innovation Review.