Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
thuc dan » thuc hanh, hoc dan, thuc vat
thuc day » thuc vat
van nham » van nam, van nhan, van tham
cao hoc » co hoc, cho hoc, chat hoc
cao hoi » cau hoi, co hoi, tao hoi
cuu tre » cua tre, cau tren, cau treo
y nang » ky nang, ly nang, v nang
vi cuu » vi luu, vinh cuu

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach y nang ((cao hoi) OR (cao hoc)). hieu van nham ((thuc day) or (thuc dan)) hanh vi cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y nang ((cao hoi) OR (cao hoc)). hieu van nham ((thuc day) OR (thuc dan)) hanh vi cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach y nang ((cao hoi) OR (cao hoc)). hieu van nham ((thuc day) or (thuc dan)) hanh vi cuu tre".
• Adding a wildcard symbol may retrieve word variants: toc sach y nang ((cao hoi) OR (cao hoc)). hieu van nham ((thuc day) or (thuc dan)) hanh vi cuu tre*.