A closed stack library contains books and other items that are not available for viewing or browsing by the general public. Many important libraries close their stacks of books to the public, limiting retrieval to professional library staff only (policies on who may use the collections varies). Most private, larger public, and university/academic/research libraries who have open stacks also have special collections that are closed. Reasons for having closed stacks vary, and include preventing theft, vandalism, and minimizing reshelving errors.