Perhaps you should try some spelling variations:
hanh dai » hanh tai, hanh dao, vanh dai
nang tai » tang tai, sang tai, nang cao
van hanh » van thanh, ban hanh, van anh
hang tai » hang va, dung tai
so sach » so sanh, bo sach, co sach
luc van » luoc van, luu van, duc van
cua tre » cua te, cuu tre, cua triet
sach v » sach va, sach y, sach 2
ve cau » ke cau, ve cac, le cau
va cau » van cau, va cac, va dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach v ((nang tai) or (hang tai)) hoa. hieu ((ve cau) OR (va cau)) luc van hanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach v ((nang tai) OR (hang tai)) hoa. hieu ((ve cau) OR (va cau)) luc van hanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach v ((nang tai) or (hang tai)) hoa. hieu ((ve cau) OR (va cau)) luc van hanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach v ((nang tai) or (hang tai)) hoa. hieu ((ve cau) OR (va cau)) luc van hanh dai cua tre*.