Perhaps you should try some spelling variations:
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
su sach » so sach, vu sach
hieu va » lieu va, hieu qua
dao hai » dao thai, dai hai, dao bai
y lang » _ lang, tay lang, yen lang
o lang » hoa lang, hoi lang
do hai » do thai, doc hai, do dai
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 (o lang)) xa hoi. hieu va cac nuoc va ((dao hai) OR (do hai)) cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((y lang) OR (o lang)) xa hoi. hieu va cac nuoc va ((dao hai) OR (do hai)) cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((y lang) or (o lang)) xa hoi. hieu va cac nuoc va ((dao hai) OR (do hai)) cua te".
• Adding a wildcard symbol may retrieve word variants: su sach ((y lang) or (o lang)) xa hoi. hieu va cac nuoc va ((dao hai) OR (do hai)) cua te*.