Students can also sell or trade textbooks among themselves. After completing a course, sellers will often seek out members of the next enrolling class, people who are likely to be interested in purchasing the required books. This may be done by posting flyers to advertise the sale of the books or simply soliciting individuals who are shopping in the college bookstore for the same titles. Many larger schools have independent websites set up for the purpose of facilitating such trade. These often operate much like digital classified ads, enabling students to list their items for sale and browse for those they wish to acquire. Also, at the US Air Force Academy, it is possible to e-mail entire specific classes, allowing for an extensive network of textbook sales to exist.