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", "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 do khi" » "so sach ky thuat do khi", "vu sach ky thuat do khi", "su sac ky thuat do khi", "su sach y thuat do khi", "su sach ty thuat do khi", "su sach ky thuat doi khi", "su sach ky thuat do thi", "su sach ky thuat bo khi", "su sach ky thuat dbo khi"
"su van ky thuat o 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 do 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 do 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 do 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 do khi") or ((("su dai ly thuat co khi") or ("su van ky thuat o khi"))))*.