Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
van hanh » van thanh, ban hanh, van anh
hanh vai » hanh vi, hanh va, hanh tai
nang ma » tang ma, nang cao, mang may
hieu va » lieu va, hieu qua
cam thu » nam thu, cac thu, ca thu
thu van » thuc van, thuy van, tu van
sang ma » tang ma, sang tao, mang may
vai dau » va dau, van dau, xvii dau
san ky » sang ky, van ky, dan ky
va cam » va cham, va cac, va cao
tu san » thu san, tu ban, tu can

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu san ky ((sang ma) or (nang ma)) hoi. hieu va cam thu van hanh vai dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu san ky ((sang ma) OR (nang ma)) hoi. hieu va cam thu van hanh vai dau tren.
• Adding a wildcard symbol may retrieve word variants: tu san ky ((sang ma) or (nang ma)) hoi. hieu va cam thu van hanh vai dau tren*.