Perhaps you should try some spelling variations:
"bo sach ky thuat do khi" » "bo sach ky thuat o khi", "co sach ky thuat do khi", "hoc sach ky thuat do khi", "bo sac ky thuat do khi", "bo sach y thuat do khi", "bo sach ty thuat do khi", "bo sach ky thuat doi khi", "bo sach ky thuat do thi", "bo sach ky thuat co khi"
"so sach ky thuat bo khi" » "so sach ky thuat bao khi", "so sach ky thuat o khi", "so sach ky thuat co khi", "so sac ky thuat bo khi", "so sach y thuat bo khi", "so sach ty thuat bo khi", "so sanh ky thuat bo khi", "co sach ky thuat bo khi", "hoc sach ky thuat bo khi", "so sach ky thuat bo chi", "so sach ky thuat bo thi"
"tu cach tam than vo thi" » "tu cach lam than vo thi", "tu cach ta than vo thi", "tu canh tam than vo thi", "tu cach ban than vo thi", "tu cac tam than vo thi", "tu cach tam than va thi", "tu cach tam than doc thi", "tu cach tam than hoc thi", "tu cach tam than do thi", "tu cach tam than vu 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: (((("bo sach ky thuat do khi") or ("so sach ky thuat bo khi"))) or ("tu cach tam than vo thi"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("bo sach ky thuat do khi") OR ("so sach ky thuat bo khi"))) OR ("tu cach tam than vo thi")).
• Removing quotes may allow a broader search: (((( bo sach ky thuat do khi ) or ( so sach ky thuat bo khi ))) or ( tu cach tam than vo thi )).
• Adding a wildcard symbol may retrieve word variants: (((("bo sach ky thuat do khi") or ("so sach ky thuat bo khi"))) or ("tu cach tam than vo thi"))*.