Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hieu van » hieu va, thien van, lieu va
hac truc » hoc truc, hang truc, sach truc
nang xa » nang x, lang xa, nang ma
van hac » van hoc, van ha, van hai
sach ky » sac ky, sach ty, sach kem
truc va » thuc va, thuc vat, trung va
cua tre » cua te, cuu tre, cua triet
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 ky) OR (sach y)) nang xa hoi. hieu van hac truc va dan vi ((cua tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sach y)) nang xa hoi. hieu van hac truc va dan vi ((cua tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) OR (sach y)) nang xa hoi. hieu van hac truc va dan vi ((cua tre) or (cau tren))".
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) OR (sach y)) nang xa hoi. hieu van hac truc va dan vi ((cua tre) or (cau tren))*.