Perhaps you should try some spelling variations:
"tu sach ki thuat duoc khi" » "tu sach ki thuat quoc khi", "tu sach ki thuat doc khi", "tu sach ki thuat do khi", "tu sach ki thuat buoc khoi", "tu sach ki thuat cuoc khoi", "tu sach ki thuat duoc kham", "thu sach ki thuat duoc khi", "su sach ki thuat duoc khi", "te sach ki thuat duoc khi", "tu sach kinh thuat duoc khi", "tu sach bai thuat duoc khi", "tu sach kem thuat duoc khi"
"tu sach ky thuat o khi" » "thu sach ky thuat o khi", "su sach ky thuat o khi", "te sach ky thuat o khi", "tu sac ky thuat o khi", "tu sach y thuat o khi", "tu sach ty thuat o khi", "tu sach ky thuat do khi", "tu sach ky thuat co khi", "tu sach ky thuat bo khi"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("tu sach ky thuat o khi") or ("tu sach ki thuat duoc khi"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("tu sach ky thuat o khi") OR ("tu sach ki thuat duoc khi")).
• Removing quotes may allow a broader search: (( tu sach ky thuat o khi ) or ( tu sach ki thuat duoc khi )).
• Adding a wildcard symbol may retrieve word variants: (("tu sach ky thuat o khi") or ("tu sach ki thuat duoc khi"))*.