Perhaps you should try some spelling variations:
khoan pho » khoan nhoi, khoan phai, khoan hoi
hoc thong » hoc thuong, hoc trong, hoc hong
pho thong » he thong
khoa hoc » hoa hoc
dai khoa » da khoa, tai khoa, dac khoa
sach dao » lanh dao
tu sach » thu sach, su sach, te sach
so sach » so sanh, bo sach, co sach
dao le » do le, dao ve, hao le
le dai » ly dai, li dai, le dan
tri te » tri le, tri ve, toi te

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