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
phu thong » pho thong, phap thong, khau thong
hanh kho » hanh khu, hang khoa, hanh theo
kho khan » khoa kham, khoa than
sach tri » sach tai, sach truc, sach bai
tri thuc » tri tue
thuc cac » thuc cach, tuc cac, phuc cac
cac khoa » cac khoan, cac khoi, dac khoa
khoa phu » khoa phau, khoa thu, hoa phu
tu sach » thu sach, te sach, tu cach
su sach » so sach, vu 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 ( su sach tri thuc cac khoa phu thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach tren thuc hanh kho khan thong ) OR ( su sach tri thuc cac khoa phu thong )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach tren thuc hanh kho khan thong ) or ( su sach tri thuc cac khoa phu thong ))*.