Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
chau tre » chay tren, chau tho, cho tre
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, ban hanh
va danh » va dinh, va dan, dia danh
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: ((toc sach) or (hoc sach)) ky nang x hoi. hieu va cac nuoc ((va hanh) OR (va danh)) lai chau tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) ky nang x hoi. hieu va cac nuoc ((va hanh) OR (va danh)) lai chau tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc sach)) ky nang x hoi. hieu va cac nuoc ((va hanh) OR (va danh)) lai chau tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) ky nang x hoi. hieu va cac nuoc ((va hanh) OR (va danh)) lai chau tre*.