Perhaps you should try some spelling variations:
ninh viet » sinh vien, anh viet
sach thu » sach thue, sach tham, cach thuc
viet cua » viec cua, viet ca, viet qua
xang mai » lang mai, sang mai, hoang mai
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
mai hoi » mai khoi, dai hoi, lai hoi
dac va » duc va, dat va, dai va
ve cac » va cac, vien cac

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: te ((sach thu) OR (sach thieu)) xang mai hoi. hieu ve cac ((dac va) or (day va)) ninh viet cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach thu) OR (sach thieu)) xang mai hoi. hieu ve cac ((dac va) OR (day va)) ninh viet cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach thu) OR (sach thieu)) xang mai hoi. hieu ve cac ((dac va) or (day va)) ninh viet cua tre*".