Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
tang tai » hang tai, dung tai, sang tao
tai khoa » da khoa, noi khoa
hieu ve » hieu va
sach ky » sac ky, sach y, sach ty
duc van » duc va, duc tan, duc manh
ky tang » ky nang, ky dang, kho tang
cuu tre » cua tre, cau tren, cau treo
te sach » toc sach

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ky tang tai khoa. ((hieu ve) or (hieu van)) pham duc van hanh tai ((cuu tre) or (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky tang tai khoa. ((hieu ve) OR (hieu van)) pham duc van hanh tai ((cuu tre) OR (dau tren)).
• Adding a wildcard symbol may retrieve word variants: te sach ky tang tai khoa. ((hieu ve) or (hieu van)) pham duc van hanh tai ((cuu tre) or (dau tren))*.