Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
sach tu » sach thu, sach ty, sach uu
hanh ki » hanh vi, hanh ky, hanh kien
va tham » van tham, va cham, va thanh
hieu va » lieu va, hieu qua
mai hoi » mai khoi, dai hoi, lai hoi
cach tu » cach thuc
so viet » hoc viet
ma hoi » xa hoi, ma hoa, me hoi
ki so » khi so, ka so, ki su

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu ((sach tu) or (cach tu)) nang ((ma hoi) or (mai hoi)). hieu va tham thuc van hanh ki so viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach tu) OR (cach tu)) nang ((ma hoi) OR (mai hoi)). hieu va tham thuc van hanh ki so viet.
• Adding a wildcard symbol may retrieve word variants: tu ((sach tu) or (cach tu)) nang ((ma hoi) or (mai hoi)). hieu va tham thuc van hanh ki so viet*.