Perhaps you should try some spelling variations:
hieu phan » phieu phan, lieu phan, hieu pham
thanh dai » thanh hai, thanh tai, thanh dat
phan dau » phan tu, hang dau
dau truc » cau truc, dai truc, doan truc
va thanh » gia thanh, ban thanh, va tinh
sach ky » sac ky, sach y, sach ty
cao hoi » cau hoi, co hoi, cao hoc
truc va » thuc va, thuc vat, trung va
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo

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 (cac ky)) nang cao hoi. hieu phan dau truc va thanh dai ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (cac ky)) nang cao hoi. hieu phan dau truc va thanh dai ((cua tre) OR (cuu tre))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (cac ky)) nang cao hoi. hieu phan dau truc va thanh dai ((cua tre) OR (cuu tre))*".