Perhaps you should try some spelling variations:
cac nuoc » hoc nuoc, dat nuoc, cua nuoc
cap nuoc » dat nuoc
su sach » so sach, vu sach
hieu va » lieu va, hieu qua
dao hai » dao thai, dai hai, do hai
hai cua » thai cua, dai cua, hoi cua
y lang » o lang, tay lang, yen lang
_ lang » o lang, _ land
va dao » ca dao
cua te » cua tu

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

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