Perhaps you should try some spelling variations:
"su dai ly thuat co khi" » "su dai my thuat co khi", "su dai ly thuyet co khi", "su dai kxy thuat co khi", "su dai ly thuat do khi", "sau dai ly thuat co khi", "si dai ly thuat co khi", "su tai ly thuat co khi", "su dai ly thuat cbo khi"
"su sach ky thuat co khi" » "su sach ky thuat do khi", "so sach ky thuat co khi", "vu sach ky thuat co khi", "su sac ky thuat co khi", "su sach y thuat co khi", "su sach ty thuat co khi", "su sach ky thuat cbo khi"
"su van ky thuat o khi" » "su van ky thuat do khi", "tu van ky thuat o khi", "vu van ky thuat o khi", "su van ky thuat bo khi"

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