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