Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
ky lang » ky nang, ky tang, tay lang
ky dang » ky nang, ky danh
hieu va » lieu va, hieu qua
cac tac » cac toc, cac bac, cac dac
dao van » do van, dang van
vat cua » mat cua, bat cua, dat cua
cua tre » cua te, cuu tre, cua triet
da van » dam van, va van, do van

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ((ky lang) or (ky dang)) xa hoi. hieu va cac tac ((da van) OR (dao van)) vat cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky dang)) xa hoi. hieu va cac tac ((da van) OR (dao van)) vat cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky lang) or (ky dang)) xa hoi. hieu va cac tac ((da van) OR (dao van)) vat cua tre*".