Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh vai » hanh vi, hanh va, hanh tai
thuc dan » thuc hanh, hoc dan, thuc vat
thuc va » thuc vat, thuc day
vai cua » dai cua, hai cua, lai cua
ty nang » ky nang, ty xang, ty hang
cua tre » cua te, cuu tre, cua triet
va cao » va cac, va co, va dao
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) or (toc sach)) ty nang x hoi. lieu va cao ((thuc va) OR (thuc dan)) hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ty nang x hoi. lieu va cao ((thuc va) OR (thuc dan)) hanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) ty nang x hoi. lieu va cao ((thuc va) OR (thuc dan)) hanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ty nang x hoi. lieu va cao ((thuc va) OR (thuc dan)) hanh vai cua tre*.