Perhaps you should try some spelling variations:
sach ngon » sach ngan, danh ngon, gach ngoi
canh ngon » danh ngon
hai thuat » phau thuat, giai thuat, khoi thuat
thuat co » thuat do, thuat o
ban ngoc » van ngoc, ban ngo, ban ngon
toan hoc » toan khoa, van hoc, hoa hoc
so ban » sao ban, so bang, co ban

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( su ((sach ngon) or (canh ngon)) ky thuat co hoc ) or ( so ban ngoc hai thuat toan hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( su ((sach ngon) OR (canh ngon)) ky thuat co hoc ) OR ( so ban ngoc hai thuat toan hoc )).
• Adding a wildcard symbol may retrieve word variants: (( su ((sach ngon) or (canh ngon)) ky thuat co hoc ) or ( so ban ngoc hai thuat toan hoc ))*.