An academic library is a library that is attached to a higher education institution which serves two complementary purposes to support the school's curriculum, and to support the research of the university faculty and students. It is unknown how many academic libraries there are internationally. An academic and research portal maintained by UNESCO links to 3,785 libraries. According to the National Center for Education Statistics, there are an estimated 3,700 academic libraries in the United States. The support of teaching and learning requires material for class readings and for student papers. In the past, the material for class readings, intended to supplement lectures as prescribed by the instructor, has been called reserves. In the period before electronic resources became available,