Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, tu cach
doan vi » doan va, don vi, doan thi
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
nang xa » nang x, lang xa, nang ma
te sach » toc sach
cac tu » cac thu, cach tu, cac du
dan vi » don vi, dan va, gan vi
ve cac » va cac, vien cac

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) OR (te sach)) ky nang xa hoi. hieu ve cac tu va ((dan vi) or (doan vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (te sach)) ky nang xa hoi. hieu ve cac tu va ((dan vi) OR (doan vi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (te sach)) ky nang xa hoi. hieu ve cac tu va ((dan vi) or (doan vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (te sach)) ky nang xa hoi. hieu ve cac tu va ((dan vi) or (doan vi)) cua tre*.