Perhaps you should try some spelling variations:
"so sanh ki thuat hoc khoi" » "so sanh ki thuat hoa khoi", "so sanh ki thuat doc khoi", "so sanh ki thuat thuc khoi", "so sanh ky thuat hoc khoi", "so sanh ki thuat hoc khoa", "so sanh ki thuat hoc hoa", "so sanh ki thuat hoc noi", "do sanh ki thuat hoc khoi"
"so sach y thuat oc khi" » "so sach y thuat doc khi", "so sach y thuat o khi", "so sach y thuat quoc khi", "bo sach y thuat oc khi", "co sach y thuat oc khi", "hoc sach y thuat oc khi", "so sach ky thuat oc khi", "so sach my thuat oc khi", "so sach kxy thuat oc khi", "so sach y thuat hoc khi", "so sach y thuat hoc khia"
"te sach y thuat do thi" » "te sach y thuat o thi", "te sach ky thuat do thi", "te sach my thuat do thi", "te sach kxy thuat do thi", "toc sach y thuat do thi"

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (((("so sanh ki thuat hoc khoi") OR ("so sach y thuat oc khi"))) OR ("te sach y thuat do thi"))~.
• Removing quotes may allow a broader search: (((( so sanh ki thuat hoc khoi ) or ( so sach y thuat oc khi ))) or ( te sach y thuat do thi ))~.
• Adding a wildcard symbol may retrieve word variants: (((("so sanh ki thuat hoc khoi") or ("so sach y thuat oc khi"))) or ("te sach y thuat do thi"))*.