Perhaps you should try some spelling variations:
"toc sach ki thuat do khi" » "hoc sach ki thuat do khi", "doc sach ki thuat do khi", "thuoc sach ki thuat do khi", "toc sach ki thuat o khi", "toc sach kinh thuat do khi", "toc sach bai thuat do khi", "toc sach kem thuat do khi", "toc sach ki thuat doi khi", "toc sach ki thuat do thi", "toc sach ki thuat bo khi"
"su sach ky thuat co khi" » "su sach ky thuat o 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 kem thuat co khi"
"su sach ty thuat co khi" » "su sach ty thuat o khi", "su sach my thuat co khi", "su sach te thuat co khi", "su sach thu thuat co khi", "so sach ty thuat co khi", "vu sach ty thuat co khi", "su sach y thuat co khi", "su sach tu thuat co 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: (("toc sach ki thuat do khi") or ((("su sach ky thuat co khi") OR ("su sach ty thuat co khi"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("toc sach ki thuat do khi") OR ((("su sach ky thuat co khi") OR ("su sach ty thuat co khi")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"toc sach ki thuat do khi\") or (((\"su sach ky thuat co khi\") OR (\"su sach ty thuat co khi\"))))".
• Removing quotes may allow a broader search: (( toc sach ki thuat do khi ) or ((( su sach ky thuat co khi ) OR ( su sach ty thuat co khi )))).
• Adding a wildcard symbol may retrieve word variants: (("toc sach ki thuat do khi") or ((("su sach ky thuat co khi") OR ("su sach ty thuat co khi"))))*.