Perhaps you should try some spelling variations:
thanh cau » thanh chau, thanh mau, nhanh cau
sach thi » sach thu, sach tai, sach thieu
nam thuc » nam thuoc, am thuc, nam thu
van hanh » van thanh, ban hanh, van ban
so triet » su triet, so thiet, bo triet
tu sach » thu sach, su sach, te sach
qua nam » quan nam, cua nam, quang nam
van anh » van thanh, tuan anh, van minh
tai so » tai sao, dai so, tai co

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 thi thanh cau hoi. hieu qua nam thuc ((van hanh) or (van anh)) tai so triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach thi thanh cau hoi. hieu qua nam thuc ((van hanh) OR (van anh)) tai so triet.
• Adding a wildcard symbol may retrieve word variants: tu sach thi thanh cau hoi. hieu qua nam thuc ((van hanh) or (van anh)) tai so triet*.