Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
dao bai » cao bai, dao lai, dap bai
dao hai » dao thai, dai hai, do hai
cua tre » cua te, cuu tre, cua triet
y lang » o lang, tay lang, yen lang
_ lang » o lang, _ land
va hoc » van hoc
nuoc » quoc, duoc, ngoc

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 ((y lang) OR (_ lang)) xa hoi. hieu va hoc nuoc va ((dao bai) or (dao hai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((y lang) OR (_ lang)) xa hoi. hieu va hoc nuoc va ((dao bai) OR (dao hai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((y lang) OR (_ lang)) xa hoi. hieu va hoc nuoc va ((dao bai) or (dao hai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((y lang) OR (_ lang)) xa hoi. hieu va hoc nuoc va ((dao bai) or (dao hai)) cua tre*.