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