Perhaps you should try some spelling variations:
khan thong » khap thong, khau thong, nhan thong
sach tren » sach tien, sach tranh
sach tri » sach tai, sach truc, sach bai
kho khan » khoa kham, khoa than
tu sach » thu sach, su sach, tu cach
va bach » va cach, va bac, va banh
te sach » toc sach
tren tu » tren tau, tran tu, tre tu
ha khan » hoa khanh, ha thanh, han khau
tu bac » tu ban, tu cac, tu bat

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: (( tu sach tri ((va bach) OR (vu bach)) kho khan thong ) OR ( te sach tren tu bac ha khan thong ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach tri ((va bach) OR (vu bach)) kho khan thong ) or ( te sach tren tu bac ha khan thong ))~".
• Adding a wildcard symbol may retrieve word variants: (( tu sach tri ((va bach) OR (vu bach)) kho khan thong ) or ( te sach tren tu bac ha khan thong ))*.