Perhaps you should try some spelling variations:
cau thuc » cau truc, cuu thuc, can thuc
hanh ki » hanh vi, hanh ky, hanh kien
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
hieu ve » hieu va, hieu van
su sach » so sach, vu sach
ty tang » tay tang, ty hang, ky tang
su viet » so viet
ma hoi » mai hoi, xa hoi, me hoi
ve cau » ke cau, va cau, ve cac
ki su » ky su

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ((ty tang) or (ty xang)) ((ma hoi) or (ma hoa)). hieu ve cau thuc va hanh ki su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ty tang) OR (ty xang)) ((ma hoi) OR (ma hoa)). hieu ve cau thuc va hanh ki su viet.
• Adding a wildcard symbol may retrieve word variants: su sach ((ty tang) or (ty xang)) ((ma hoi) or (ma hoa)). hieu ve cau thuc va hanh ki su viet*.