Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hanh vai » hanh vi, hanh va, hanh tai
tu sach » thu sach, su sach, te sach
tu nang » tru nang, tu nano, tu lang
tu nong » tu dong, tu cong, tu tong
van cam » van nam, van lam, van cau
luc van » luoc van, luu van, duc van
vai cua » dai cua, hai cua, lai cua
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 sach ((tu nang) OR (tu nong)) xa hoi. hieu van cam ((luc van) or (duc tan)) hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((tu nang) OR (tu nong)) xa hoi. hieu van cam ((luc van) OR (duc tan)) hanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((tu nang) OR (tu nong)) xa hoi. hieu van cam ((luc van) or (duc tan)) hanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((tu nang) OR (tu nong)) xa hoi. hieu van cam ((luc van) or (duc tan)) hanh vai cua tre*.