Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
hanh dai » hanh tai, hanh dao, vanh dai
van hanh » van thanh, ban hanh, van anh
tao khoi » tao hoi, thao khoa, lao khoa
thuc van » thuc vat, thuc dan, thuc va
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
tai hoi » tai khoi, dai hoi, tai hai
hieu ve » hieu va
cua te » cua tu
y nang » ky nang, ly nang, v nang

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