Perhaps you should try some spelling variations:
thien van » thi van
dinh vai » dinh van, dinh vi, dinh va
tu sach » thu sach, su sach, te sach
lang xa » lang ha, dang xay, lang van
hieu va » lieu va
cau duc » cao duc, cau luc, chu duc
va dinh » van dinh, va kinh, va tinh
vai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet
sach o » sach lo, sac o, sach y
o lang » hoa lang, hoi lang

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