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