Some Online eTextbooks come with supplemental Companion Materials included in the purchase price. These might be downloadable files or access to on-line resources such as a companion website.
Companion Materials are listed on the eTextbook's Product Information page, and also at the right-hand side of the Reader when the eTextbook is open.
Some Companion Materials are access-protected and require an Access Code. In this case, follow the directions in Obtaining an Access Code for an eResource.