Perhaps you should try some spelling variations:
cach khoan » cac khoan, cach hoan, bach khoa
khoan phai » khong phai, khoa phau, khoan hoi
phai thong » phap thong, phai tuong, phan thong
thuc cach » thuoc sach, truoc cach, thuc hanh
sach dai » sach dao, sach bai, sach dat
dai thuc » dan thuc, dai thu, dai thua
cac khoa » cac khoan, cac khoi, dac khoa
te sach » toc sach
tu lanh » tu hanh, tu lenh, tu manh
dao hoc » dai hoc, dan hoc, day hoc
hoc cac » hoc cao
khoa he » hoa he, khoa hoc, khong he

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 dai thuc cach khoan phai thong ) or ( tu lanh dao hoc cac khoa he thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( te sach dai thuc cach khoan phai thong ) OR ( tu lanh dao hoc cac khoa he thong )).
• Adding a wildcard symbol may retrieve word variants: (( te sach dai thuc cach khoan phai thong ) or ( tu lanh dao hoc cac khoa he thong ))*.