Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
ty nang » ky nang, ty xang, ty hang
va pham » van pham, va phat, va phap
dan dai » dat dai, can dai, dan dat
cua tre » cua te, cuu tre, cua triet
va dan » ca dan, va dao, va dau
x hoi » xa hoi, o hoi, 5 hoi

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