Perhaps you should try some spelling variations:
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va
va hanh » van hanh, va thanh, va danh
hanh ve » hanh vi, hanh va, hanh kem
ca tren » cau tren, cu tren, la tren
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky
ve ca » ve cac, ve cai, ve cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sac ky ((nang ma) or (nang x)) hoi. ((hieu va) OR (hieu qua)) pham duc va hanh ve ca tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky ((nang ma) OR (nang x)) hoi. ((hieu va) OR (hieu qua)) pham duc va hanh ve ca tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky ((nang ma) or (nang x)) hoi. ((hieu va) OR (hieu qua)) pham duc va hanh ve ca tren".
• Adding a wildcard symbol may retrieve word variants: tu sac ky ((nang ma) or (nang x)) hoi. ((hieu va) OR (hieu qua)) pham duc va hanh ve ca tren*.