Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
hieu van » hieu va, thien van, lieu va
truc va » thuc vat, trung va
dai cuu » dai cua, dai huu
thuc va » thuc vat, thuc dan, thuc day
van cau » van dau, van hau, van chat
sach ky » sach y, sach ty, sach kem
cao hoi » cau hoi, co hoi, cao hoc
cuu tre » cua tre, cau tren, cau treo
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 cau ((truc va) OR (thuc va)) thanh dai cuu 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 cau ((truc va) OR (thuc va)) thanh dai cuu 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 cau ((truc va) OR (thuc va)) thanh dai cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sac ky)) nang cao hoi. hieu van cau ((truc va) OR (thuc va)) thanh dai cuu tre*.