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
cam loc » cam lo
loc van » luoc van, hoc van, lo van
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
va lang » va nang, hoa lang
o lang » hoa lang, hoi lang
va cam » va cham, va cac, va cao

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 cam 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 cam loc van ((hanh dai) OR (hanh dao)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((va lang) or (o lang)) xa hoi. hieu va cam 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 cam loc van ((hanh dai) OR (hanh dao)) cua tre*.