Perhaps you should try some spelling variations:
hieu hieu » hien hieu, hieu hien, thien hieu
hieu cac » hieu luc, hieu va, hieu van
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
vai cua » dai cua, hai cua, lai cua
va danh » va dinh, va hanh, dia danh
tu sach » thu sach, su sach, te sach
ty nang » ky nang, ty hang, ly nang
cua tre » cua te, cuu tre, cua triet
va dan » ca dan, va dao, va dau

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

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