Perhaps you should try some spelling variations:
cac truc » cau truc, cac tru, cac trung
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
cua tre » cua te, cua triet, dua tren
truc va » thuc va, thuc vat, trung va
van cac » van hac, van cau, van bac
ly vang » ly hang, ly van, ly quang
ly nang » ky nang, ly hang, ly quang
cuu tre » cau tren, cau treo
va don » va dong, va doc, va do

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 ((ly nang) OR (ly vang)) xa hoi. hieu van cac truc va don vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ly nang) OR (ly vang)) xa hoi. hieu van cac truc va don vi ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ly nang) OR (ly vang)) xa hoi. hieu van cac truc va don vi ((cua tre) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: su sach ((ly nang) OR (ly vang)) xa hoi. hieu van cac truc va don vi ((cua tre) or (cuu tre))*.