Perhaps you should try some spelling variations:
tham thuc » pham thuc, tam thuc, thai thuc
nham thuc » nhan thuc, nam thuc, nham thu
tai khoi » tai khoa, mai khoi, tao khoi
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
hanh dai » hanh tai, hanh dao, vanh dai
su sach » so sach, vu sach
tai hoi » dai hoi, tai hai, tai hoe
y nang » ky nang, ly nang, v nang
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 y nang ((tai hoi) or (tai khoi)). hieu van ((tham thuc) OR (nham 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 (tai khoi)). hieu van ((tham thuc) OR (nham 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 (tai khoi)). hieu van ((tham thuc) OR (nham thuc)) van hanh dai cua te".
• Adding a wildcard symbol may retrieve word variants: su sach y nang ((tai hoi) or (tai khoi)). hieu van ((tham thuc) OR (nham thuc)) van hanh dai cua te*.