Perhaps you should try some spelling variations:
"bo sach ki thuat hoc khoi" » "bo sach ki thuat hoa khoi", "bo sach ki thuat doc khoi", "bo sach ki thuat thuc khoi", "bo sach ky thuat hoc khoi", "bo sach ki thuat hoc khoa", "bo sach ki thuat hoc hoa", "bo sach ki thuat hoc noi", "co sach ki thuat hoc khoi", "hoc sach ki thuat hoc khoi", "bo sach kinh thuat hoc khoi", "bo sach bai thuat hoc khoi", "bo sach kem thuat hoc khoi"
"so sach y thuat hoc ki" » "so sach y thuat hoa ki", "so sach y thuat doc ki", "so sach y thuat thuc ki", "so sanh y thuat hoc ki", "co sach y thuat hoc ki", "hoc sach y thuat hoc ki", "so sach ky thuat hoc ki", "so sach my thuat hoc ki", "so sach kxy thuat hoc ki", "so sach y thuat hoc ky", "so sach y thuat hoc kinh"
"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: (((("bo sach ki thuat hoc khoi") OR ("so sach y thuat hoc ki"))) OR ("te sach y thuat do thi"))~.
• Removing quotes may allow a broader search: (((( bo sach ki thuat hoc khoi ) or ( so sach y thuat hoc ki ))) or ( te sach y thuat do thi ))~.
• Adding a wildcard symbol may retrieve word variants: (((("bo sach ki thuat hoc khoi") or ("so sach y thuat hoc ki"))) or ("te sach y thuat do thi"))*.