Perhaps you should try some spelling variations:
hanh gian » thanh gian, thanh giang, manh giang
so sanh » do sanh
cua tre » cuu tre, cua triet, dua tren
va hanh » van hanh, va thanh, va danh
sanh ky » hanh ky, sang ky, nganh ky
hieu va » lieu va, hieu qua
nang ma » sang ma, nang cao, mang may
tang ma » mang may, tang van
bai bo » bac bo, ban bo, bai mo
cua te » cua tu
bo va » bao va, do va, so va

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sanh ky ((nang ma) or (tang ma)) hoi. hieu va bai bo va hanh gian ((cua tre) OR (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sanh ky ((nang ma) OR (tang ma)) hoi. hieu va bai bo va hanh gian ((cua tre) OR (cua te)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sanh ky ((nang ma) or (tang ma)) hoi. hieu va bai bo va hanh gian ((cua tre) OR (cua te))".
• Adding a wildcard symbol may retrieve word variants: so sanh ky ((nang ma) or (tang ma)) hoi. hieu va bai bo va hanh gian ((cua tre) OR (cua te))*.