Perhaps you should try some spelling variations:
khoan phai » khong phai, khoa phau, khoan hoi
phai thong » phap thong, phai tuong, phan thong
cau khoan » cuu khoa, cu khoa, cau hoa
sach dao » lanh dao
khoan he » khoa he, khoan ke, khoan le
toc sach » hoc sach, doc sach, thuoc sach
sach thi » sach thu, sach tai, sach thieu
tu sach » thu sach, su sach, te sach
dao tue » dao tuc, dao tuyen, dao tuyet
tue cac » tu cac, tuc cac, te cac
thi le » thi lien
le cau » ke cau, le mau, le cap

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 dao tue cac khoan he thong ) OR ( toc sach thi le cau khoan phai thong ))~.
• Adding a wildcard symbol may retrieve word variants: (( tu sach dao tue cac khoan he thong ) or ( toc sach thi le cau khoan phai thong ))*.