Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, hieu ve
phat duc » pham duc, phan duc, phan duoc
van hanh » van thanh, ban hanh, van anh
hanh tai » thanh tai, hang tai, han tai
so sach » bo sach, co sach, hoc sach
so sanh » do sanh
ty nang » ky nang, ty xang, ty hang
duc van » duc va, duc tan, duc manh
tai cua » thai cua, tai cuc, tri cua
cua te » cua tu
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((so sach) OR (so sanh)) ty nang x hoi. ((hieu van) or (lieu va)) phat duc van hanh tai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((so sach) OR (so sanh)) ty nang x hoi. ((hieu van) OR (lieu va)) phat duc van hanh tai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((so sach) OR (so sanh)) ty nang x hoi. ((hieu van) or (lieu va)) phat duc van hanh tai cua te".
• Adding a wildcard symbol may retrieve word variants: ((so sach) OR (so sanh)) ty nang x hoi. ((hieu van) or (lieu va)) phat duc van hanh tai cua te*.