Perhaps you should try some spelling variations:
"su sach kxy thuat do thi" » "su sach ki thuat do thi", "su sach my thuat do thi", "su sach ky thua do thi", "su sach kxy thuat o thi", "su sach xa thuat do thi", "su sach kem thuat do thi", "su sac ky thuat do thi", "so sach kxy thuat do thi", "vu sach kxy thuat do thi"
"vu bach va thuat bo khi" » "vu bach ki thuat bo khi", "vu bach va thuc bo khi", "vu bach va thiet bo khi", "vu bach va thuat bao khi", "vu bach va thuat o khi", "vu bach va thuat co khi", "vu bach van thuat bo khi", "vu bach ha thuat bo khi", "vu sach va thuat bo khi", "vu bach va thuat bo chi", "vu bach va thuat bo thi"
"tu cach ky thuat do thi" » "tu cach ky thuat o thi", "tu cac ky 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: (("vu bach va thuat bo khi") or ((("tu cach ky thuat do thi") or ("su sach kxy thuat do thi"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("vu bach va thuat bo khi") OR ((("tu cach ky thuat do thi") OR ("su sach kxy thuat do thi")))).
• Removing quotes may allow a broader search: (( vu bach va thuat bo khi ) or ((( tu cach ky thuat do thi ) or ( su sach kxy thuat do thi )))).
• Adding a wildcard symbol may retrieve word variants: (("vu bach va thuat bo khi") or ((("tu cach ky thuat do thi") or ("su sach kxy thuat do thi"))))*.