Perhaps you should try some spelling variations:
sach thi » sach thu, sach tai, sach tham
hieu va » lieu va, hieu qua
cac luc » cau luc, coc luc, cac nuoc
va tinh » may tinh
tinh di » tinh doi, trinh di, tinh da
cuu tre » cau tren, cau treo
cua tre » cua te, cua triet, dua tren
hang o » hang do, hang o2, hoang o
luc va » duc va, tuc va, loc va
o hoi » co hoi, o hoc, o hai

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

• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach thi) OR (sach thieu)) hang o hoi. hieu va cac luc va tinh di ((cuu tre) OR (cua tre))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach thi) OR (sach thieu)) hang o hoi. hieu va cac luc va tinh di ((cuu tre) or (cua tre))~".
• Adding a wildcard symbol may retrieve word variants: te ((sach thi) OR (sach thieu)) hang o hoi. hieu va cac luc va tinh di ((cuu tre) or (cua tre))*.