Perhaps you should try some spelling variations:
thien van » thi van
thu sach » tu sach, thuat sach, thuoc sach
van dau » van dao, phan dau
cuu tre » cua tre, cau tren, cau treo
ty nang » ky nang, ty hang, ly nang
dau va » dau ve
vi cuu » vi luu, vinh cuu
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: thu sach ((ty nang) or (ty xang)) o hoi. thien van dau ((dau va) OR (lau va)) hanh vi cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((ty nang) OR (ty xang)) o hoi. thien van dau ((dau va) OR (lau va)) hanh vi cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ((ty nang) or (ty xang)) o hoi. thien van dau ((dau va) OR (lau va)) hanh vi cuu tre".
• Adding a wildcard symbol may retrieve word variants: thu sach ((ty nang) or (ty xang)) o hoi. thien van dau ((dau va) OR (lau va)) hanh vi cuu tre*.