Perhaps you should try some spelling variations:
cach khoan » cac khoan, cach hoan, bach khoa
sach tren » sach tien, sach tranh
tren thuc » trien thuc, tron thuc, trinh thuc
thuc hang » thuc hanh, thu hang, phuc hang
hang khoa » dung khoa
thuc cach » thuoc sach, truoc cach, thuc hanh
khoan cay » khoan cam, khoan va, khoa cam
te sach » toc sach
khoa he » hoa he, khoa hoc, khong he
tu sach » thu sach, su sach, tu cach

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( te sach tren thuc hang khoa he thong ) or ( tu sach tren thuc cach khoan cay trong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( te sach tren thuc hang khoa he thong ) OR ( tu sach tren thuc cach khoan cay trong )).
• Adding a wildcard symbol may retrieve word variants: (( te sach tren thuc hang khoa he thong ) or ( tu sach tren thuc cach khoan cay trong ))*.