Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
hieu van » hieu va, thien van, hieu ve
va thanh » gia thanh, ban thanh, va tinh
sach ky » sach y, sach ty, sach kem
cao hoi » cau hoi, co hoi, cao hoc
truc va » thuc va, thuc vat, trung va
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky

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 ky) or (sac ky)) nang cao hoi. ((hieu van) OR (lieu va)) cau truc va thanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) nang cao hoi. ((hieu van) OR (lieu va)) cau truc va thanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (sac ky)) nang cao hoi. ((hieu van) OR (lieu va)) cau truc va thanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sac ky)) nang cao hoi. ((hieu van) OR (lieu va)) cau truc va thanh dai cua tre*.