Perhaps you should try some spelling variations:
giao duoc » giao duc, giac duoc, tao duoc
duoc khoa » nuoc khoa, duc khoa, huoc khoa
khoa hoc » hoa hoc
quanh em » anh em, quan am, quanh _
tu sach » thu sach, su sach, te sach
so sach » so sanh, bo sach, hoc sach
co sach » bo sach, cuon sach, hoc sach
quan ao » quan so, quang cao, quang bao

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) or (((so sach) OR (co sach)))) giao duoc khoa hoc - stem. stem ((quanh em) or (quan ao))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (((so sach) OR (co sach)))) giao duoc khoa hoc - stem. stem ((quanh em) OR (quan ao)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (((so sach) OR (co sach)))) giao duoc khoa hoc - stem. stem ((quanh em) or (quan ao))".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (((so sach) OR (co sach)))) giao duoc khoa hoc - stem. stem ((quanh em) or (quan ao))*.