Perhaps you should try some spelling variations:
"vu sach ky thuat co khi" » "vu sach ky thuat o khi", "vu bach ky thuat co khi", "vu khach ky thuat co khi", "vu sac ky thuat co khi", "vu sach y thuat co khi", "vu sach ty thuat co khi"
"su sach ki thuat bo khi" » "su sach ki thuat bao khi", "su sach ki thuat o khi", "su sach ki thuat so khi", "su sach kinh thuat bo khi", "su sach bai thuat bo khi", "su sach kem thuat bo khi", "su sach ki thuat bo chi", "su sach ki thuat bo thi"
"so sach ky thuat do khi" » "so sach ky thuat o khi", "so sac ky thuat do khi", "so sach y thuat do khi", "so sach ty thuat do khi", "so sanh ky thuat do khi", "bo sach ky thuat do khi", "co sach ky thuat do khi", "so sach ky thuat doi khi", "so sach ky thuat do thi", "so sach ky thuat dong khi"

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

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