Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
hanh dao » lanh dao, thanh dat, thanh dam
hieu voi » hieu moi, lieu voi, hieu loi
su sach » so sach, vu sach
thuc va » thuc vat, thuc dan, thuc day
tai hoi » tai khoi, tai hai, tai hoe
dao cua » dai cua, day cua, dan cua
dai hoi » dai hoc, dai hai, dai moi
hien vi » hien dai
sach ky » sac ky, sach y, sach ty
va hanh » van hanh, va thanh, va danh
cua te » cua tu

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 ky nang ((tai hoi) OR (dai hoi)). ((hien vi) or (hieu voi)) tham thuc va hanh dao cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((tai hoi) OR (dai hoi)). ((hien vi) OR (hieu voi)) tham thuc va hanh dao cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((tai hoi) OR (dai hoi)). ((hien vi) or (hieu voi)) tham thuc va hanh dao cua te".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((tai hoi) OR (dai hoi)). ((hien vi) or (hieu voi)) tham thuc va hanh dao cua te*.