Perhaps you should try some spelling variations:
nang doc » nang luc
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
hieu ve » hieu va, hieu van
nang du » nang tu, nang luc
cua tre » cua te, cuu tre, cua triet
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky
ve cac » va cac, vien cac
bao va » bao ve, tao va, cao va

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sac ky lang xa hoi. hieu ve cac ((bao va) or (ban va)) ((nang du) OR (nang doc)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky lang xa hoi. hieu ve cac ((bao va) OR (ban va)) ((nang du) OR (nang doc)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky lang xa hoi. hieu ve cac ((bao va) or (ban va)) ((nang du) OR (nang doc)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sac ky lang xa hoi. hieu ve cac ((bao va) or (ban va)) ((nang du) OR (nang doc)) cua tre*.