Perhaps you should try some spelling variations:
thanh dat » thanh san, thanh hai, thanh van
lang van » dang van, tang van, hoang van
hanh dao » lanh dao, thanh dam, doanh dao
tu sach » thu sach, su sach, te sach
cua tre » cua te, cuu tre, cua triet
cao duc » dao duc, cao suc, giao duc
hieu va » lieu va, hieu qua
lang ha » long ha
va cao » va cac, va co, va dao

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