Perhaps you should try some spelling variations:
thien van » thi van
tinh dai » trinh dai, tinh da, tinh doi
tinh hai » tinh thai, tinh chat, trinh han
tu sach » thu sach, su sach, te sach
cua tre » cua te, cuu tre, cua triet
y lang » o lang, tay lang, yen lang
_ lang » o lang, _ land
van am » van nam, van lam, van dam
am hoc » ad hoc

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) or (_ lang)) xa hoi. thien van am hoc va ((tinh dai) OR (tinh hai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((y lang) OR (_ lang)) xa hoi. thien van am hoc va ((tinh dai) OR (tinh hai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((y lang) or (_ lang)) xa hoi. thien van am hoc va ((tinh dai) OR (tinh hai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((y lang) or (_ lang)) xa hoi. thien van am hoc va ((tinh dai) OR (tinh hai)) cua tre*.