Perhaps you should try some spelling variations:
"vu sach ky thuat o khi" » "vu bach ky thuat o khi", "su sach ky thuat o khi", "vu khach ky thuat o khi", "vu sac ky thuat o khi", "vu sach y thuat o khi", "vu sach ty thuat o khi", "vu sach ky thuat bo khi"
"su xac ky thuat co khi" » "pu xac ky thuat co khi", "su cac ky thuat co khi", "su sac ky thuat co khi", "su bac ky thuat co khi", "su xac ky thuat cbo khi"
"su sai ky thuat do thi" » "su tai ky thuat do thi", "su hai ky thuat do thi", "su dai ky thuat do thi", "su sac ky 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: (("su xac ky thuat co khi") or ((("vu sach ky thuat o khi") or ("su sai ky thuat do thi"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("su xac ky thuat co khi") OR ((("vu sach ky thuat o khi") OR ("su sai ky thuat do thi")))).
• Removing quotes may allow a broader search: (( su xac ky thuat co khi ) or ((( vu sach ky thuat o khi ) or ( su sai ky thuat do thi )))).
• Adding a wildcard symbol may retrieve word variants: (("su xac ky thuat co khi") or ((("vu sach ky thuat o khi") or ("su sai ky thuat do thi"))))*.