Perhaps you should try some spelling variations:
thanh hoi » thanh hoai, thanh hoa, thanh hai
van thanh » ban thanh, van tuan
tu sach » thu sach, te sach, tu cach
hoi cua » hoi chuc
duc van » duc va, duc tan, duc manh
cac duc » cac du, cao duc, cac dac
qua cac » cua cac
lang xa » lang ha, dang xay, lang van
nang xa » nang x, nang ma, mang xa
su sach » so sach, vu sach
cua tre » cua te, cuu tre, cua triet

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 (su sach)) lo ((nang xa) OR (lang xa)) hoi. hieu qua cac duc van thanh hoi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) lo ((nang xa) OR (lang xa)) hoi. hieu qua cac duc van thanh hoi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (su sach)) lo ((nang xa) OR (lang xa)) hoi. hieu qua cac duc van thanh hoi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) lo ((nang xa) OR (lang xa)) hoi. hieu qua cac duc van thanh hoi cua tre*.