Perhaps you should try some spelling variations:
"te sach kxy thuat o khi" » "te sach my thuat o khi", "te sach ky thua o khi", "te sach xa thuat o khi", "te sach kem thuat o khi", "te sac ky thuat o khi", "te sach kxy thuat co khi", "te sach kxy thuat bo khi"
"toc sach ky thuat dco khi" » "toc sach ky thuat co khi", "toc sach ky thuat dao khi", "toc sach ky thuat duoc khi", "hoc sach ky thuat dco khi", "doc sach ky thuat dco khi", "thuoc sach ky thuat dco khi", "toc sac ky thuat dco khi", "toc sach y thuat dco khi", "toc sach ty thuat dco khi", "toc sach ky thuat dcco khi", "toc sach ky thuat dcbo khi"
"tu sach ki thuat do 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"

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: (((("te sach kxy thuat o khi") or ("toc sach ky thuat dco khi"))) or ("tu sach ki thuat do thi"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("te sach kxy thuat o khi") OR ("toc sach ky thuat dco khi"))) OR ("tu sach ki thuat do thi")).
• Removing quotes may allow a broader search: (((( te sach kxy thuat o khi ) or ( toc sach ky thuat dco khi ))) or ( tu sach ki thuat do thi )).
• Adding a wildcard symbol may retrieve word variants: (((("te sach kxy thuat o khi") or ("toc sach ky thuat dco khi"))) or ("tu sach ki thuat do thi"))*.