23. Basic Grammar in Use Student Book with Answers : 한국어판 (Paperback, 3rd Edition) - Self-Study Reference and Practice for Students of North American English - Cambridge In Use 2
37. Grammar in Use Intermediate Student's Book with Answers and Interactive eBook : Self-study Reference and Practice for Students of American English (Multiple-component retail product, 4 Revised edition) - Cambridge In Use 36
43. Grammar in Use Intermediate Student's Book with Answers : Self-study Reference and Practice for Students of American English (Paperback, 4 Revised edition) - Cambridge In Use 35