Perhaps you should try some spelling variations:
hac truc » hoc truc, hang truc, sach truc
hieu van » hieu va, thien van, lieu va
cua tre » cua te, cua triet, dua tren
truc va » thuc va, thuc vat, trung va
van hac » van hoc, van ha, van hai
su sach » so sach, vu sach
lang xa » lang ha, dang xay, lang van
nang xa » nang x, nang ma, mang xa
cuu tre » cau tren, cau treo
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va

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