Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
van cac » van hac, van cau, van bac
cua tre » cua te, cuu tre, cua triet
cac tu » cac thu, cach tu, cac du
dan vi » doan vi, gan vi, dan ve
dan va » doan va, dan ca, ban va
x hoi » xa hoi, o hoi, x ho

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 ky nang x hoi. hieu van cac tu va ((((dan vi) or (dan va))) or (don vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x hoi. hieu van cac tu va ((((dan vi) OR (dan va))) OR (don vi)) cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x hoi. hieu van cac tu va ((((dan vi) or (dan va))) or (don vi)) cua tre*.