Perhaps you should try some spelling variations:
khoi thuat » ki thuat, hoc thuat
kxy thuat » ky thuat, ki thuat, my thuat
sach khoi » sach hoi, bach khoa, cach thoi
thuat do » thuat o
sach kxy » sach xa, sach kem, sac ky
tu sach » thu sach, te sach, tu cach
y thuat » ky thuat, my thuat, ki thuat
su sach » so sach, vu sach
do khi » doi khi, do thi, co 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 y thuat do khi ) or ((( su sach kxy thuat do khi ) or ( su sach khoi thuat do khi ))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach y thuat do khi ) OR ((( su sach kxy thuat do khi ) OR ( su sach khoi thuat do khi )))).
• Adding a wildcard symbol may retrieve word variants: (( tu sach y thuat do khi ) or ((( su sach kxy thuat do khi ) or ( su sach khoi thuat do khi ))))*.