Perhaps you should try some spelling variations:
thuat doi » thuat do, thuat di, thuat doc
sach kxy » sach kem, sach y, sach hay
tu sach » thu sach, su sach, te sach
sach ky » sach y, sach ty, sach kem
thuat o » thuat do
sach xa » sach dao, sach nha, sach bai
sac ky » cac ky, sai ky
o khi » co khi, bo khi

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 o khi ) or ( su ((((sach kxy) OR (sach xa))) or (sac ky)) thuat doi khi ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach ky thuat o khi ) OR ( su ((((sach kxy) OR (sach xa))) OR (sac ky)) thuat doi khi )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach ky thuat o khi ) or ( su ((((sach kxy) OR (sach xa))) or (sac ky)) thuat doi khi ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach ky thuat o khi ) or ( su ((((sach kxy) OR (sach xa))) or (sac ky)) thuat doi khi ))*.