In today's classrooms, teachers have difficulty making knowledge from a broad range of sources available to students. Few experts are readily available in the school. Students do not have access to experts outside the school either. In fact, it's even a special event whenever an outside expert comes to visit even though those experts are often not really all that expert.
In today's schools, access to knowledge largely means access to books. But it's time-consuming and difficult for students to locate the specific parts of the specific books that contain the information they want. Most students have had the experience of finding a source that gives an interesting lead, but then they have to dig up three other sources to pursue that lead.
Where am I in the content of the book?