1. 索书单：cafeteria 自助小餐厅 | call slip 索书单 | campus 校园
2. 借书单：date slip 期限单 | call slip 借书单 | bibliography 著者检索目录
3. 借书证：call round 偶然拜访 | call slip 借书证 | call someone back 回电给
1. They must fill in a call slip to obtain books after presenting valid certificates.