Perhaps you should try some spelling variations:
trinh co » trinh cong, trinh hoa, trinh ky
trinh do » trinh ky
khoa hoc » hoa hoc
thu sach » thuat sach, thuoc sach, thu hoach
sach dao » lanh dao
mai khoa » tai khoa, may khoa, dai khoa
tu sach » su sach, te sach, tu cach
dao mai » dao bai, dao hai, dao lai

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tu sach ((trinh co) OR (trinh do)) khoa hoc ) or ( thu sach dao mai khoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach ((trinh co) OR (trinh do)) khoa hoc ) OR ( thu sach dao mai khoa hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach ((trinh co) OR (trinh do)) khoa hoc ) or ( thu sach dao mai khoa hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach ((trinh co) OR (trinh do)) khoa hoc ) or ( thu sach dao mai khoa hoc ))*.