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