Perhaps you should try some spelling variations:
khan thong » khap thong, khau thong, nhan thong
sach tren » sach tien, sach tranh
tren thuc » trien thuc, tron thuc, trinh thuc
sach truc » cach thuc, sach thu, sach thue
truc chua » truc chuoi, thuc cua, truc nha
pho thong » he thong
hanh kho » hanh khu, hang khoa, hanh theo
kho khan » khoa kham, khoa than
chua cau » cua cau, chua cu, chua dau
cau khoi » cau hoi, cac khoi, cau thi
khoi pho » khoi tho, khoi khoa, hoc pho
tu sach » thu sach, su sach, te sach

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tu sach tren thuc hanh kho khan thong ) or ( tu sach truc chua cau khoi pho thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach tren thuc hanh kho khan thong ) OR ( tu sach truc chua cau khoi pho thong )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach tren thuc hanh kho khan thong ) or ( tu sach truc chua cau khoi pho thong ))*.