Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
dang hai » dang khai, hang hai, dung hai
ban dang » ban hang, ban dan, van dang
dang xay » dang van, van xay
cao duc » dao duc, cao suc, giao duc
hai cua » thai cua, dai cua, hoi cua
hieu ve » hieu va, hieu van
xay hoi » xa hoi, tay hoi, cay phoi
ky dang » ky nang, ky danh
cua tre » cua te, cuu tre, cua triet

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 (doc sach)) ky dang xay hoi. hieu ve ((cao duc) or (pham duc)) ban dang hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ky dang xay hoi. hieu ve ((cao duc) OR (pham duc)) ban dang hai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) ky dang xay hoi. hieu ve ((cao duc) or (pham duc)) ban dang hai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) ky dang xay hoi. hieu ve ((cao duc) or (pham duc)) ban dang hai cua tre*.