Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
dan hanh » dang hanh, dan khanh, dan thanh
tu cach » tu cac
su sach » so sach, vu sach
nang xa » nang x, lang xa, nang ma
dan anh » dan canh, van anh, lan anh
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu cach) or (su sach)) ky nang xa hoi. hieu van nam thuc ((dan anh) OR (dan hanh)) dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu cach) OR (su sach)) ky nang xa hoi. hieu van nam thuc ((dan anh) OR (dan hanh)) dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu cach) or (su sach)) ky nang xa hoi. hieu van nam thuc ((dan anh) OR (dan hanh)) dai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu cach) or (su sach)) ky nang xa hoi. hieu van nam thuc ((dan anh) OR (dan hanh)) dai cua tre*.