Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
hanh ca » hanh cac, hanh cat, hanh cua
van cam » van nam, van lam, van cau
te sach » toc sach
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
xuc va » duc va, luc va, xac va
tuc va » thuc va, truc va, tuc xa
ca cua » co cua
o hoi » co hoi, o hoc, o hai

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) or (te sach)) ky nang o hoi. hieu van cam ((xuc va) OR (tuc va)) hanh ca cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (te sach)) ky nang o hoi. hieu van cam ((xuc va) OR (tuc va)) hanh ca cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (te sach)) ky nang o hoi. hieu van cam ((xuc va) OR (tuc va)) hanh ca cua tre".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (te sach)) ky nang o hoi. hieu van cam ((xuc va) OR (tuc va)) hanh ca cua tre*.