Perhaps you should try some spelling variations:
dau tieng » dau tien, cau tieng, day tieng
cac thoi » cac toi, cac hop, cac tro
hanh tai » thanh tai, hang tai, han tai
hieu van » hieu va, thien van, lieu va
ky tang » ky nang, ky dang, kho tang
van cam » van nam, van lam, van cau
cam duc » cam xuc, cao duc, pham duc
va hanh » van hanh, va thanh, va danh
ky lang » ky nang, ky dang, tay lang
cuu tre » cua tre, cau tren, cau treo
tu sach » thu sach, su sach, te sach

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky tang)) cac thoi. 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 lang) OR (ky tang)) cac thoi. hieu van cam duc va hanh tai ((cuu tre) or (dau tieng))~".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky lang) OR (ky tang)) cac thoi. hieu van cam duc va hanh tai ((cuu tre) or (dau tieng))*.