Perhaps you should try some spelling variations:
"tu sach tien tu cach thoi he thong" » "tu sach thieu tu cach thoi he thong", "tu sach tien tu cac thoi he thong", "tu sach tien tu cach thuc he thong", "tu sach tien tu cach noi he thong", "thu sach tien tu cach thoi he thong", "su sach tien tu cach thoi he thong", "vu sach tien tu cach thoi he thong", "tu sach thien tu cach thoi he thong", "tu sach tien thu cach thoi he thong", "tu sach dien tu cach thoi he thong", "tu sach tien tu cach khoi he thong", "tu sach tien tu cach thoi hien thong", "tu sach tien tu cach thoai hy thong"
"te sach tren thuc hanh khoa hoc cong" » "te sach tranh thuc hanh khoa hoc cong", "te sach trien thuc hanh khoa hoc cong", "te sach tron thuc hanh khoa hoc cong", "te sach trinh thuc hanh khoa hoc cong", "te sach tren thuc hang khoa hoc cong", "te sach tren thuc anh khoa hoc cong", "te sach tren thuc hanh hoa hoc cong", "te sach tren thuc hanh khoa hoc co", "te sach tren thuc hanh khoa cac cong", "te sach tren thuc hanh khoa hoc dung", "toc sach tren thuc hanh khoa hoc cong"

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: (("tu sach tien tu cach thoi he thong") or ("te sach tren thuc hanh khoa hoc cong"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("tu sach tien tu cach thoi he thong") OR ("te sach tren thuc hanh khoa hoc cong")).
• Removing quotes may allow a broader search: (( tu sach tien tu cach thoi he thong ) or ( te sach tren thuc hanh khoa hoc cong )).
• Adding a wildcard symbol may retrieve word variants: (("tu sach tien tu cach thoi he thong") or ("te sach tren thuc hanh khoa hoc cong"))*.