Methods, systems, and apparatus, including computer program products are provided for responding to search queries having results that identify books. In one aspect, a search query and multiple web pages that satisfy the search query and have a ranked order as responses to the search query are received. A subset of web pages that are each a reference page for a respective book are selected. A web page is a reference page for a book when the web page includes a reference to the book and satisfies a citation criterion for the book. A book score is assigned to each of the books for which there is at least one reference page in the group of highest ranking web pages. The book scores are used to select one or more of the books. A book reference is generated for each of the books and the book references are provided in response to the search query.