Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
cam thuc » am thuc, nam thuc, cam thu
dang mam » dang nam, dang mau, dang mat
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
dang ma » dang mau, dang mat, tang ma
sac ky » cac ky, sai ky
va cua » va chua, via cua, ca cua
te sac » te sach, te cac, te san

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sac ky ((dang ma) or (dang mam)) hoi. ((hieu van) or (hieu va)) cam thuc va hanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sac ky ((dang ma) OR (dang mam)) hoi. ((hieu van) OR (hieu va)) cam thuc va hanh va cua tre.
• Adding a wildcard symbol may retrieve word variants: te sac ky ((dang ma) or (dang mam)) hoi. ((hieu van) or (hieu va)) cam thuc va hanh va cua tre*.