Perhaps you should try some spelling variations:
cac truc » cau truc, cac tru, cac trung
hanh tai » thanh tai, hang tai, hinh tai
ly quang » le quang, vu quang
truc va » thuc va, thuc vat, trung va
han tai » hang tai, nhan tai, van tai
co sach » bo sach, cuon sach, hoc sach
hieu va » lieu va, hieu qua
duc tre » duoc tren, duc tien

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

• Performing a fuzzy search may retrieve terms with similar spellings: co sach ((ly hang) or (ly quang)) xa hoi. hieu va cac truc va ((hanh tai) OR (han tai)) duc tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach ((ly hang) OR (ly quang)) xa hoi. hieu va cac truc va ((hanh tai) OR (han tai)) duc tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "co sach ((ly hang) or (ly quang)) xa hoi. hieu va cac truc va ((hanh tai) OR (han tai)) duc tre".
• Adding a wildcard symbol may retrieve word variants: co sach ((ly hang) or (ly quang)) xa hoi. hieu va cac truc va ((hanh tai) OR (han tai)) duc tre*.