Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh dai » hanh tai, hanh dao, vanh dai
va lang » va nang, hoa lang
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
o lang » hoa lang, hoi lang
va cam » va cham, va cac, va cao
cam lo » nam lo, cam ly, cam o
lo va » lo van, lao va, ly va

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 lo va hanh dai 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 lo va hanh dai cua tre.
• Adding a wildcard symbol may retrieve word variants: toc sach ((va lang) or (o lang)) xa hoi. hieu va cam lo va hanh dai cua tre*.