Perhaps you should try some spelling variations:
"bo sach ky thuat doc khi" » "bo sach ky thuat duoc khi", "bo sach ky thuat doi khi", "bo sach ky thuat quoc khi", "bo sach ky thuat oc khi", "co sach ky thuat doc khi", "hoc sach ky thuat doc khi", "bo sac ky thuat doc khi", "bo sach ty thuat doc khi", "bo sach kem thuat doc khi", "bo sach ky thuat hoc khi", "bo sach ky thuat hoc khoi", "bo sach kmy thuat doc khi", "bo sach kkxy thuat doc khi", "bo sach kki thuat doc khi"
"so sac kki thuat don khi" » "so sac ki thuat don khi", "so sac khoi thuat don khi", "so sac mi thuat don khi", "so sac kki thuat dong khi", "so sac kki thuat dan khi", "so sac kki thuat doi khi", "so sac kki thuat on khi", "so sac kki thuat duong khi", "so sach kki thuat don khi", "so dac kki thuat don khi"
"te sach y thuat do thi" » "te sach y thuat o thi", "toc sach y thuat do thi", "te sach my thuat do thi", "te sach kxy thuat do thi", "te sach ki 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: (((("bo sach ky thuat doc khi") or ("so sac kki thuat don khi"))) or ("te sach y thuat do thi"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("bo sach ky thuat doc khi") OR ("so sac kki thuat don khi"))) OR ("te sach y thuat do thi")).
• Removing quotes may allow a broader search: (((( bo sach ky thuat doc khi ) or ( so sac kki thuat don khi ))) or ( te sach y thuat do thi )).
• Adding a wildcard symbol may retrieve word variants: (((("bo sach ky thuat doc khi") or ("so sac kki thuat don khi"))) or ("te sach y thuat do thi"))*.