Perhaps you should try some spelling variations:
"vu bach kxy thuat _ khi" » "vu bach ki thuat _ khi", "vu bach my thuat _ khi", "vu bach ky thua _ khi", "vu bac ky thuat _ khi", "vu bach kxmy thuat _ khi", "vu bach kxki thuat _ khi", "vu bach kxva thuat _ khi"
"su sach y thuat co khi" » "su sach y thuat o khi", "so sach y thuat co khi", "vu sach y thuat co khi", "su sach my thuat co khi", "su sach ki thuat co khi", "su sach va thuat co khi"
"su sach ky thuat do khi" » "su sach ky thuat o khi", "so sach ky thuat do khi", "vu sach ky thuat do khi", "su sach kmy thuat do khi", "su sach kki thuat do khi", "su sach kva thuat do khi", "su sac ky thuat do khi", "su sach ty thuat do khi", "su sach kem thuat do khi", "su sach ky thuat doi khi", "su sach ky thuat do thi", "su sach ky thuat bo khi"

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (("su sach y thuat co khi") OR ((("vu bach kxy thuat _ khi") OR ("su sach ky thuat do khi"))))~.
• Removing quotes may allow a broader search: (( su sach y thuat co khi ) or ((( vu bach kxy thuat _ khi ) or ( su sach ky thuat do khi ))))~.
• Adding a wildcard symbol may retrieve word variants: (("su sach y thuat co khi") or ((("vu bach kxy thuat _ khi") or ("su sach ky thuat do khi"))))*.