Perhaps you should try some spelling variations:
sach tien » sach tren, sach thieu
tien ban » thien ban, trien ban, dien ban
dua tren » dung tren
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
dinh vi » dinh ve, dinh viet, dinh tri
va dinh » van dinh, va kinh, va tinh
cam tuc » cam xuc, cam tu, nam thuc
van cam » van nam, van lam, van cau
cuu tre » cua tre, cau tren, cau treo
va hoc » van hoc
tuc va » thuc va, truc va, tuc xa
va hoi » xa hoi, va hoa

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 tien ban ((va hoi) OR (va hoc)). hieu van cam tuc va dinh vi ((dua tren) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach tien ban ((va hoi) OR (va hoc)). hieu van cam tuc va dinh vi ((dua tren) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach tien ban ((va hoi) OR (va hoc)). hieu van cam tuc va dinh vi ((dua tren) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: su sach tien ban ((va hoi) OR (va hoc)). hieu van cam tuc va dinh vi ((dua tren) or (cuu tre))*.