Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
lang tai » lang thai, hang tai, tang tai
tai khoa » da khoa, noi khoa
hanh tai » thanh tai, hang tai, han tai
hieu van » hieu va, thien van, lieu va
cuu tre » cua tre, cau tren, cau treo
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va
ky lang » ky nang, ky dang, ky tang

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 lang tai khoa. ((hieu ve) OR (hieu van)) pham duc va hanh tai ((cuu tre) or (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang tai khoa. ((hieu ve) OR (hieu van)) pham duc va hanh tai ((cuu tre) OR (dau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky lang tai khoa. ((hieu ve) OR (hieu van)) pham duc va hanh tai ((cuu tre) or (dau tren))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang tai khoa. ((hieu ve) OR (hieu van)) pham duc va hanh tai ((cuu tre) or (dau tren))*.