Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
truc may » tren may, truc va
sach thu » sach thue, sach thieu, sach tham
tinh va » tich va, trinh van, trinh vat
hieu ke » hieu kem, chieu ke, hieu ky
sach ty » sach y, sach tu, xach tay
ke cau » ket cau
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, o hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: so ((sach ty) or (sach thu)) xang ((o hoi) or (o hai)). hieu ke cau truc may tinh va su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach ty) OR (sach thu)) xang ((o hoi) OR (o hai)). hieu ke cau truc may tinh va su triet.
• Adding a wildcard symbol may retrieve word variants: so ((sach ty) or (sach thu)) xang ((o hoi) or (o hai)). hieu ke cau truc may tinh va su triet*.