Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc anh
thanh di » thanh doi, thanh de, thanh do
nuoc gia » nuoc giai, nuoc giao, quoc gia
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
hieu va » lieu va, hieu qua
va nang » van nang, da nang, cam nang
hoc cac » hoc cao
vu nang » vuc nang, vu dang, v nang
cua tre » cua te, cuu tre, cua triet
di cua » dai cua, doi cua, de cua
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: ((hoc sach) or (hoc cac)) ((vu nang) OR (va nang)) x hoi. hieu va cac nuoc gia thanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((hoc sach) OR (hoc cac)) ((vu nang) OR (va nang)) x hoi. hieu va cac nuoc gia thanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((hoc sach) or (hoc cac)) ((vu nang) OR (va nang)) x hoi. hieu va cac nuoc gia thanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: ((hoc sach) or (hoc cac)) ((vu nang) OR (va nang)) x hoi. hieu va cac nuoc gia thanh di cua tre*.