Perhaps you should try some spelling variations:
"tu sach ki thuat do thi" » "tu sach ki thuat o thi", "thu sach ki thuat do thi", "su sach ki thuat do thi", "tu cach ki thuat do thi", "tu sach kinh thuat do thi", "tu sach bai thuat do thi", "tu sach kem thuat do thi"
"so sach y thuat co khi" » "so sach y thuat o khi", "so sanh y thuat co khi", "bo sach y thuat co khi", "co sach y thuat co khi", "so sach my thuat co khi", "so sach kxy thuat co khi", "so sach va thuat co khi"
"te sach ky thuat co khi" » "te sach ky thuat o khi", "te sach kmy thuat co khi", "te sach kkxy thuat co khi", "te sach kva thuat co khi", "toc sach ky thuat co khi", "te sac ky thuat co khi", "te sach ty thuat co khi", "te sach kem 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: (("tu sach ki thuat do thi") or ((("so sach y thuat co khi") or ("te sach ky thuat co khi"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("tu sach ki thuat do thi") OR ((("so sach y thuat co khi") OR ("te sach ky thuat co khi")))).
• Removing quotes may allow a broader search: (( tu sach ki thuat do thi ) or ((( so sach y thuat co khi ) or ( te sach ky thuat co khi )))).
• Adding a wildcard symbol may retrieve word variants: (("tu sach ki thuat do thi") or ((("so sach y thuat co khi") or ("te sach ky thuat co khi"))))*.