Perhaps you should try some spelling variations:
"so sanh ve thuat duoc khi" » "so sanh ve thuat quoc khi", "so sanh ve luat duoc khi", "so sanh ve xuat duoc khi", "so sanh va thuat duoc khi", "so sanh ki thuat duoc khi", "so sanh my thuat duoc khi", "so sanh ve thuat buoc khoi", "so sanh ve thuat cuoc khoi", "so sanh ve thuat duoc kham", "do sanh ve thuat duoc khi", "so hanh ve thuat duoc khi", "so anh ve thuat duoc khi"
"bo sach ky thuat doc khi" » "bo sach ky thuat doi khi", "bo sach ky thuat don 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"
"toc sach y thuat do thi" » "hoc sach y thuat do thi", "doc sach y thuat do thi", "thuoc sach y thuat do thi", "toc sach y thuat o thi", "toc sach my thuat do thi", "toc sach kxy thuat do thi", "toc 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 sanh ve thuat duoc khi"))) or ("toc 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 sanh ve thuat duoc khi"))) OR ("toc sach y thuat do thi")).
• Removing quotes may allow a broader search: (((( bo sach ky thuat doc khi ) or ( so sanh ve thuat duoc khi ))) or ( toc sach y thuat do thi )).
• Adding a wildcard symbol may retrieve word variants: (((("bo sach ky thuat doc khi") or ("so sanh ve thuat duoc khi"))) or ("toc sach y thuat do thi"))*.