Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
hieu van » thien van, lieu va, hieu ve
tu sach » thu sach, su sach, te sach
cau duc » cao duc, cau luc, chu duc
duc van » duc va, duc tan, duc manh
cua tre » cua te, cuu tre, cua triet
sach ty » sach y, sach tu, sach thu
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
ty lang » tay lang, ty xang, ty hang

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