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