Perhaps you should try some spelling variations:
sach tham » sach nha
sach thue » sach thu, sach thieu, cach thuc
thanh cau » thanh chau, thanh mau, nhanh cau
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 thiet » soc thiet, hoc thiet, hoa thiet
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 tham) or (sach thue)) thanh cau hoi. hieu qua nam thuc van hanh tai so thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach tham) OR (sach thue)) thanh cau hoi. hieu qua nam thuc van hanh tai so thiet.
• Adding a wildcard symbol may retrieve word variants: tu ((sach tham) or (sach thue)) thanh cau hoi. hieu qua nam thuc van hanh tai so thiet*.