Perhaps you should try some spelling variations:
"so sach ky thuat hoc khoi" » "so sach ky thuat hoa khoi", "so sach ky thuat thuc khoi", "so sach ky thuat phuc khoi", "so sach ky thuat hoc khoa", "so sach ky thuat hoc hoa", "so sach ky thuat hoc noi", "bo sach ky thuat hoc khoi", "co sach ky thuat hoc khoi", "hoc sach ky thuat hoc khoi", "so sac ky thuat hoc khoi", "so sach y thuat hoc khoi", "so sach ty thuat hoc khoi"
"so sanh ky thuat doc khi" » "so sanh ky thuat duoc khi", "so sanh ky thuat doi khi", "so sanh ky thuat don khi", "so sanh ky thuat oc khi", "do sanh ky thuat doc khi", "so hanh ky thuat doc khi", "so sang ky thuat doc khi", "so nganh ky thuat doc khi", "so sanh ky thuat hoc khi", "so sanh ky thuat dong khi"
"te sach kxy thuat do thi" » "te sach ki thuat do thi", "te sach my thuat do thi", "te sach ky thua do thi", "te sach xa thuat do thi", "te sach kem thuat do thi", "te sac ky thuat do thi", "te sach kxy thuat o thi", "toc sach kxy thuat do thi"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (((("so sanh ky thuat doc khi") or ("so sach ky thuat hoc khoi"))) or ("te sach kxy thuat do thi"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("so sanh ky thuat doc khi") OR ("so sach ky thuat hoc khoi"))) OR ("te sach kxy thuat do thi")).
• Removing quotes may allow a broader search: (((( so sanh ky thuat doc khi ) or ( so sach ky thuat hoc khoi ))) or ( te sach kxy thuat do thi )).
• Adding a wildcard symbol may retrieve word variants: (((("so sanh ky thuat doc khi") or ("so sach ky thuat hoc khoi"))) or ("te sach kxy thuat do thi"))*.