Perhaps you should try some spelling variations:
canh trinh » canh tranh, hanh trinh, canh tinh
sach ngan » sach ngon, sach nha, sach han
trinh ly » trinh ky, trinh do, trinh tu
ly thuat » my thuat, ly thuyet, kxy thuat
toan hoc » toan khoa, van hoc, tin hoc
tu sach » thu sach, su sach, te sach
ngan ky » nganh ky, nhan ky, ngan hay
thuat o » thuat do
tu canh » thu canh, tu chanh, tu can
o hoc » co hoc, mo hoc, so 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 ( tu canh trinh ly thuat ((toan hoc) or (hoa hoc)) ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach ngan ky thuat o hoc ) OR ( tu canh trinh ly thuat ((toan hoc) OR (hoa hoc)) )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach ngan ky thuat o hoc ) or ( tu canh trinh ly thuat ((toan hoc) or (hoa hoc)) ))*.