Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh dao » lanh dao, thanh dat, thanh dam
hanh dai » hanh tai, vanh dai, thanh dat
loc van » luoc van, hoc van, lo van
cac loc » cac lop, cac toc, cac hoc
hieu va » lieu va, hieu qua
va lang » va nang, hoa lang
cua tre » cua te, cuu tre, cua triet
o lang » hoa lang, hoi lang

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 ((va lang) or (o lang)) xa hoi. hieu va cac loc van ((hanh dai) or (hanh dao)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((va lang) OR (o lang)) xa hoi. hieu va cac loc van ((hanh dai) OR (hanh dao)) cua tre.
• Adding a wildcard symbol may retrieve word variants: toc sach ((va lang) or (o lang)) xa hoi. hieu va cac loc van ((hanh dai) or (hanh dao)) cua tre*.