To find e-books in the library catalog, go to Advanced Search and limit by Collection to Ebooks. Then enter your search terms.
This link will take you to a search of all e-books in the catalog with the keyword sustainab*. The asterisk is a wildcard, causing the computer to search for any word that starts with sustainab*: sustainable, sustainability, etc.
Below are some examples of electronic reference books on Sustainability. You can locate reference e-books by including search terms such as encyclopedia, dictionary, guide and handbook in conjunction with "sustainab*" or "environmen*"