Perhaps you should try some spelling variations:
dau tieng » dau tien, cau tieng, day tieng
cac khoi » cac thoi, cac khoan, cach thoi
hanh tai » thanh tai, hang tai, han tai
hieu van » hieu va, thien van, lieu va
lang cac » bang cac, hang cac, dang cac
sach ky » sac ky, sach ty, sach kem
van cam » van nam, van lam, van cau
cam duc » cam xuc, cao duc, pham duc
va hanh » van hanh, va thanh, va danh
cuu tre » cua 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 (sach y)) lang cac khoi. hieu van cam duc va hanh tai ((cuu tre) or (dau tieng))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach y)) lang cac khoi. hieu van cam duc va hanh tai ((cuu tre) OR (dau tieng)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sach y)) lang cac khoi. hieu van cam duc va hanh tai ((cuu tre) or (dau tieng))".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sach y)) lang cac khoi. hieu van cam duc va hanh tai ((cuu tre) or (dau tieng))*.