Perhaps you should try some spelling variations:
"su hai kki thuat co khi" » "su hai ki thuat co khi", "su hai khoi thuat co khi", "su hai ky thuat co khi", "su phai khi thuat co khi", "su thai khi thuat co khi", "su tai kki thuat co khi", "su hai kki thuat cbo khi"
"su sach kxy thuat o khi" » "su sach ky thuat o khi", "su sach ki thuat o khi", "su sach ky thua o khi", "su sach xa thuat o khi", "su sach kem thuat o khi", "su sac ky thuat o khi", "so sach kxy thuat o khi", "vu sach kxy thuat o khi", "su sach kxy thuat bo khi"
"su xac my thuat do thi" » "su xac ky thuat do thi", "su xac ki thuat do thi", "su xac va thuat do thi", "pu xac my thuat do thi", "su cac my thuat do thi"

Try widening your search to All Fields.

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

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