Perhaps you should try some spelling variations:
"so sac ky thuat hoc khoi" » "so sac ky thuat hoa khoi", "so sac ky thuat thuc khoi", "so sac ky thuat phuc khoi", "so sac ky thuat hoc khoa", "so sac ky thuat hoc hoa", "so sac ky thuat hoc noi", "so dac ky thuat hoc khoi", "so cac ky thuat hoc khoi", "so sai ky 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 sach y thuat doc khi", "so sach ty thuat doc khi", "so sach kem thuat doc khi", "so sach ky thuat hoc khi", "so sach ky thuat dong khi", "so dach ky thuat doc khi"
"te sach ki thuat do thi" » "te sach ki thuat o thi", "toc sach ki thuat do thi", "te sach kinh thuat do thi", "te sach bai thuat do thi", "te sach kem 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 sac ky thuat hoc khoi"))) or ("te sach ki thuat do thi"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("so sach ky thuat doc khi") OR ("so sac ky thuat hoc khoi"))) OR ("te sach ki thuat do thi")).
• Removing quotes may allow a broader search: (((( so sach ky thuat doc khi ) or ( so sac ky thuat hoc khoi ))) or ( te sach ki thuat do thi )).
• Adding a wildcard symbol may retrieve word variants: (((("so sach ky thuat doc khi") or ("so sac ky thuat hoc khoi"))) or ("te sach ki thuat do thi"))*.