Perhaps you should try some spelling variations:
canh trinh » canh tranh, hanh trinh, canh tinh
sach ngan » sach ngon, sach nha, sach han
hay thuat » phau thuat, ky thuat, my thuat
trinh kxy » trinh ky, trinh ly, trinh ke
kxy thuat » ky thuat, ki thuat, my thuat
ngan hay » ngan han, ngan hang, nganh xay
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
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 hay 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 ngan hay thuat o hoc ) OR ( tu canh trinh kxy thuat ((toan hoc) OR (hoa hoc)) )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach ngan hay thuat o hoc ) or ( tu canh trinh kxy thuat ((toan hoc) or (hoa hoc)) ))*.