Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
cam quoc » cac quoc, cao quoc, nam quoc
hoc sach » hoc sinh, hoc cac, hoc anh
ban hanh » ban hang
quoc ban » quoc bao, quoc lan, quoc quan
hieu van » thien van, lieu va, hieu ve
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
y lang » o lang, _ lang, tay lang
di cua » dai cua, doi cua, de cua

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)) y lang xa hoi. ((hieu van) or (hieu va)) cam quoc ban hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) y lang xa hoi. ((hieu van) OR (hieu va)) cam quoc ban hanh di cua tre.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) y lang xa hoi. ((hieu van) or (hieu va)) cam quoc ban hanh di cua tre*.