Perhaps you should try some spelling variations:
sach tay » xach tay, sach hay, sach tai
hanh vai » hanh vi, hanh va, hanh tai
sach nay » sach hay, sach vay, sach nang
hieu van » hieu va, thien van, lieu va
van cau » van dau, van hau, van chat
lang xa » lang ha, dang xay, lang van
su tien » su kien, su hien, tu tieng
luc va » duc va, tuc va, loc va
vai su » va su, van su, lai su

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 tay) or (sach nay)) lang xa hoi. hieu van cau ((luc va) or (hoc va)) hanh vai su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach tay) OR (sach nay)) lang xa hoi. hieu van cau ((luc va) OR (hoc va)) hanh vai su tien.
• Adding a wildcard symbol may retrieve word variants: su ((sach tay) or (sach nay)) lang xa hoi. hieu van cau ((luc va) or (hoc va)) hanh vai su tien*.