Perhaps you should try some spelling variations:
trien khai » trien nha
tien khoi » tien khi, tien khoan, tien khong
hai khoa » thai khoa, chai khoa, tai khoa
khoa hoc » hoa hoc
te sach » toc sach
sach xa » sach dao, sach nha, sach bai
tu sach » thu sach, su sach, tu cach
xa hai » xa thai, xua hai, xa hoi

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (( te sach xa hai khoa hoc ) OR ( tu sach ((tien khoi) OR (trien khai)) khoa hoc ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( te sach xa hai khoa hoc ) or ( tu sach ((tien khoi) OR (trien khai)) khoa hoc ))~".
• Adding a wildcard symbol may retrieve word variants: (( te sach xa hai khoa hoc ) or ( tu sach ((tien khoi) OR (trien khai)) khoa hoc ))*.