The university has four libraries housing more than million books, as well as electronic resources including e-books, serial titles, and databases.  Three of the libraries are on campus: the Dana Porter Library, housing material relating to arts, humanities and social science, the Davis Centre Library, housing material for engineering, mathematics and science, and the Witer Learning Resource Centre, housing material for the School of Optometry and Vision Science. The fourth library, the Musagetes Architecture Library, is in Cambridge, alongside the university's School of Architecture . The libraries of the university's affiliated colleges are also considered a part of the university's library system.  The university's library system is also a member of the TriUniversity Group, a partnership between the University of Guelph , University of Waterloo and Wilfrid Laurier University. The group provides students and researchers at all three universities with access to all of the collections and services.  The group also operates the TUG Annex, a repository for less-used library resources from the three universities.