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", "so sanh ky thuat hoc khoi", "bo sach ky thuat hoc khoi", "co sach ky thuat hoc khoi", "so sac ky thuat hoc khoi", "so sach y thuat hoc khoi", "so sach ty thuat hoc khoi"
"so sach ky thuat doc khi" » "so sach ky thuat duoc khi", "so sach ky thuat doi khi", "so sach ky thuat don khi", "so sach ky thuat oc khi", "so sanh ky thuat doc khi", "bo sach ky thuat doc khi", "co sach ky thuat doc khi", "so sac ky thuat doc khi", "so sach y thuat doc khi", "so sach ty thuat doc khi", "so sach ky thuat hoc khi", "so sach 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 sach 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 sach 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 sach 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 sach ky thuat doc khi") or ("so sach ky thuat hoc khoi"))) or ("te sach kxy thuat do thi"))*.