Perhaps you should try some spelling variations:
sach tranh » canh tranh
kki thuat » khoi thuat, ky thuat, mi thuat
sach dan » sach danh, sach dao, sach dat
ki thuat » ky thuat
tu sach » thu sach, su sach, te sach
y thuat » ky thuat, my thuat, kxy thuat
thuat o » thuat do
dan y » dan ky, dan _, day y
o hoc » co hoc, mo hoc, so hoc
toan » tran

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 dan y thuat o hoc ) or ( tu sach tranh ((kki thuat) OR (ki thuat)) toan khoa ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach dan y thuat o hoc ) OR ( tu sach tranh ((kki thuat) OR (ki thuat)) toan khoa )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach dan y thuat o hoc ) or ( tu sach tranh ((kki thuat) OR (ki thuat)) toan khoa ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach dan y thuat o hoc ) or ( tu sach tranh ((kki thuat) OR (ki thuat)) toan khoa ))*.