Perhaps you should try some spelling variations:
sach thue » sach thu, sach thieu, sach tham
thanh dan » thanh san, thanh van, thanh dat
vat thanh » dat thanh, gat thanh, tat thanh
sach thuc » cach thuc, sach thu, sach truc
hieu van » hieu va, thien van, lieu va
hoc vat » hoc va, hoc viet, thuc vat
van cau » van dau, van hau, van chat
cau hoc » cau hoi, cau hoa, cao hoc
hanh ca » hanh cac, hanh cat, hanh cua
ca hoi » cau hoi, cua hoi, xa hoi
cua tu » cua tuc, cua su, cua cu

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 thuc) OR (sach thue)) hanh ca hoi. hieu van cau hoc vat thanh dan ((cua te) OR (cua tu))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach thuc) OR (sach thue)) hanh ca hoi. hieu van cau hoc vat thanh dan ((cua te) or (cua tu))~".
• Adding a wildcard symbol may retrieve word variants: te ((sach thuc) OR (sach thue)) hanh ca hoi. hieu van cau hoc vat thanh dan ((cua te) or (cua tu))*.