Perhaps you should try some spelling variations:
thanh cau » thanh chau, thanh mau, nhanh cau
sach thi » sach tai, sach thieu, sach tham
sach thu » sach thue, sach thieu, sach tham
nam thuc » nam thuoc, am thuc, nam thu
thuc van » thuc vat, thuc dan, thuc va
van hanh » van thanh, ban hanh, van anh
hanh tai » thanh tai, hang tai, han tai
so triet » su triet, so thiet, bo triet
qua nam » quan nam, cua nam, quang nam
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) or (sach thu)) thanh cau hoi. hieu qua nam thuc van hanh tai so triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach thi) OR (sach thu)) thanh cau hoi. hieu qua nam thuc van hanh tai so triet.
• Adding a wildcard symbol may retrieve word variants: tu ((sach thi) or (sach thu)) thanh cau hoi. hieu qua nam thuc van hanh tai so triet*.