Perhaps you should try some spelling variations:
sach tren » sach tien, sach tranh
khoan pho » khoan nhoi, khoan phai, khoan hoi
sach dao » lanh dao
dai khoa » da khoa, tai khoa, dac khoa
so sach » so sanh, bo sach, co sach
tren te » tien te, tren xe, tren he
su sach » vu sach
khoa he » hoa he, khoa hoc, khong he
te cac » tu cac, ve cac, te cao
dao ve » bao ve, dap ve, dau ve
ve dai » vi dai, va dai, he dai

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( so sach tren te cac khoan pho thong ) or ( su sach dao ve dai khoa he thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( so sach tren te cac khoan pho thong ) OR ( su sach dao ve dai khoa he thong )).
• Adding a wildcard symbol may retrieve word variants: (( so sach tren te cac khoan pho thong ) or ( su sach dao ve dai khoa he thong ))*.