Perhaps you should try some spelling variations:
sach hay » sach han, sach ha, sach nay
hieu van » hieu va, thien van, lieu va
chua tre » chua tri, cua tre, chua trieu
so sach » so sanh, bo sach, co sach
cong ha » cong hoa, cong tac, cong san
dong ha » dong hoa, dong va, dong hoc
van lam » van nam
vi chua » va chua, vi khuan, chi chua
xuc va » tuc va, luc va, xac va

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 hay ((cong ha) OR (dong ha)) hoi. hieu van lam ((xuc va) or (duc va)) hanh vi chua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach hay ((cong ha) OR (dong ha)) hoi. hieu van lam ((xuc va) OR (duc va)) hanh vi chua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach hay ((cong ha) OR (dong ha)) hoi. hieu van lam ((xuc va) or (duc va)) hanh vi chua tre".
• Adding a wildcard symbol may retrieve word variants: so sach hay ((cong ha) OR (dong ha)) hoi. hieu van lam ((xuc va) or (duc va)) hanh vi chua tre*.