Perhaps you should try some spelling variations:
canh trinh » hanh trinh, canh tinh, anh trinh
sach ngan » sach ngon, sach nha, sach han
kxy thuat » ki thuat, my thuat, ky thua
thuat do » thuat o
toan hoc » toan khoa, van hoc, hoa hoc
tu sach » thu sach, su sach, te sach
ngan ky » nganh ky, nhan ky, ngan hay
do hoc » co hoc, do hoa, du hoc
tranh » thanh, tran, trang

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 ngan ky thuat do hoc ) or ( tu ((canh trinh) OR (canh tranh)) kxy thuat toan hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach ngan ky thuat do hoc ) OR ( tu ((canh trinh) OR (canh tranh)) kxy thuat toan hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach ngan ky thuat do hoc ) or ( tu ((canh trinh) OR (canh tranh)) kxy thuat toan hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach ngan ky thuat do hoc ) or ( tu ((canh trinh) OR (canh tranh)) kxy thuat toan hoc ))*.