Perhaps you should try some spelling variations:
"hoc sach dinh thuc hanh kho khan thong" » "hoc sach dinh thuc hanh kho khap thong", "hoc sach dinh thuc hanh kho nhan thong", "hoc sach dinh thuc hanh kho phan thong", "hoc sach kinh thuc hanh kho khan thong", "hoc sach danh thuc hanh kho khan thong", "hoc hoach dinh thuc hanh kho khan thong", "hoc sach dinh thuy hanh kho khan thong", "hoc sach dinh chuc hanh kho khan thong", "hoc sach sinh thuc hanh kho khan thong", "hoc sinh dinh thuc hanh kho khan thong", "hoc cac dinh thuc hanh kho khan thong", "hoc anh dinh thuc hanh kho khan thong", "hoc sach dinh thuc hanh khu khan thong", "hoc sach dinh thuc hang khoa khan thong", "hoc sach dinh thuc hanh theo khan thong", "hoc sach dinh thuc hanh khoa kham thong", "hoc sach dinh thuc hanh khoa than thong"
"hoc sach tham thuc cach khoa khau thong" » "hoc sach tham thuc cach khoa khau thuong", "hoc sach tham thuc cach khoa khap thong", "hoc sach tham thuc cach khoa khau tong", "hoc sach nha thuc cach khoa khau thong", "hoc sach nham thuc cach khoa khau thong", "hoc sach pham thuc cach khoa khau thong", "hoc sach tam thuc cach khoa khau thong", "hoc sach tham thuoc sach khoa khau thong", "hoc sach tham truoc cach khoa khau thong", "hoc sach tham tuc cac khoa khau thong", "hoc sach tham thuc bach khoa khau thong", "hoc sach tham thuc cac khoa khau thong", "hoc sach tham thuc cac khoan khau thong", "hoc sach tham thuc cach khoa kham thong", "hoc sach tham thuc cach khoa phau thong", "hoc sach tham thuc cach khoa chau thong", "hoc sinh tham thuc cach khoa khau thong", "hoc cac tham thuc cach khoa khau thong", "hoc anh tham thuc cach khoa khau thong"

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("hoc sach dinh thuc hanh kho khan thong") or ("hoc sach tham thuc cach khoa khau thong"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("hoc sach dinh thuc hanh kho khan thong") OR ("hoc sach tham thuc cach khoa khau thong")).
• Removing quotes may allow a broader search: (( hoc sach dinh thuc hanh kho khan thong ) or ( hoc sach tham thuc cach khoa khau thong )).
• Adding a wildcard symbol may retrieve word variants: (("hoc sach dinh thuc hanh kho khan thong") or ("hoc sach tham thuc cach khoa khau thong"))*.