Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
cau tren » cu tren, dau tren, ca tren
su sach » so sach, vu sach
sach tu » sach thu, cach tu, sach ty
tu nang » tru nang, tu nong, tu nano
nang xa » nang x, lang xa, nang ma
van cau » van dau, van hau, van chat
duc ban » duc van, dua ban, duc man
cua tre » cua te, cuu tre, cua triet

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 tu nang xa hoi. hieu van cau ((duc ban) OR (duc tan)) hanh vi ((cua tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach tu nang xa hoi. hieu van cau ((duc ban) OR (duc tan)) hanh vi ((cua tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach tu nang xa hoi. hieu van cau ((duc ban) OR (duc tan)) hanh vi ((cua tre) or (cau tren))".
• Adding a wildcard symbol may retrieve word variants: su sach tu nang xa hoi. hieu van cau ((duc ban) OR (duc tan)) hanh vi ((cua tre) or (cau tren))*.