Perhaps you should try some spelling variations:
"su sach ky thuat do khi" » "su sach ky thuat o khi", "so sach ky thuat do khi", "vu sach ky thuat do khi", "su sac ky thuat do khi", "su sach y thuat do khi", "su sach ty thuat do khi", "su sach ky thuat doi khi", "su sach ky thuat co khi", "su sach ky thuat bo khi"
"tu xach tay than do thi" » "tu canh tay than do thi", "tu xach tam than do thi", "tu xach tay thai do thi", "tu xach bay than do thi", "tu hach tay than do thi", "tu sach tay than do thi", "tu xach tay thanh do thi", "tu xach tay than vo thi", "tu xach tay phan do thi"
"tu cach ta than doc thi" » "tu cach ta thanh doc thi", "tu cach ta than voc thi", "tu cach ta phan doc thi", "tu cac ta than doc thi", "tu cach tu than doc thi", "tu cach pha than doc thi", "tu cach bao than doc thi", "tu cach tam than doc thi", "tu cach te than doc thi", "tu cach ta than duc thi", "tu cach ta than doan thi", "tu cach ta than dong thi"

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("su sach ky thuat do khi") or ((("tu xach tay than do thi") or ("tu cach ta than doc thi"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("su sach ky thuat do khi") OR ((("tu xach tay than do thi") OR ("tu cach ta than doc thi")))).
• Removing quotes may allow a broader search: (( su sach ky thuat do khi ) or ((( tu xach tay than do thi ) or ( tu cach ta than doc thi )))).
• Adding a wildcard symbol may retrieve word variants: (("su sach ky thuat do khi") or ((("tu xach tay than do thi") or ("tu cach ta than doc thi"))))*.