Perhaps you should try some spelling variations:
canh trinh » canh tranh, hanh trinh, canh tinh
sach ngan » sach ngon, sach nha, sach han
trinh kxy » trinh ky, trinh ly, trinh ke
kxy thuat » ki thuat, my thuat, ky thua
toan hoc » toan khoa, van hoc, hoa hoc
tu sach » thu sach, su sach, te sach
ngan ky » nganh ky, nhan ky, ngan hay
tu canh » thu canh, tu chanh, tu can
o hoc » mo hoc, so hoc, y hoc

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