Perhaps you should try some spelling variations:
hanh dao » lanh dao, thanh dat, thanh dam
hanh dai » hanh tai, vanh dai, thanh dat
cua tre » cua te, cuu tre, cua triet
cac duc » cac du, cao duc, cac dac
qua cac » cua cac
nang ma » tang ma, sang ma, nang cao
sang xa » song xa, lang xa, sang ma
sac ky » cac ky, sai ky
tu sac » tu sach, tu cac, tu san

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 ((sang xa) or (nang ma)) hoi. hieu qua cac duc va ((hanh dai) OR (hanh dao)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky ((sang xa) OR (nang ma)) hoi. hieu qua cac duc va ((hanh dai) OR (hanh dao)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky ((sang xa) or (nang ma)) hoi. hieu qua cac duc va ((hanh dai) OR (hanh dao)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sac ky ((sang xa) or (nang ma)) hoi. hieu qua cac duc va ((hanh dai) OR (hanh dao)) cua tre*.