Perhaps you should try some spelling variations:
sach tranh » canh tranh
kxy thuat » ky thuat, ki thuat, my thuat
tranh cai » tranh cac, trinh cai, tranh chap
cai thuat » cac thuat, giai thuat, ki thuat
sach day » sach dao, sach dat, sach dau
su sach » so sach, vu sach
o hoc » mo hoc, so hoc, y 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: (( su sach day kxy thuat ((o hoc) or (co hoc)) ) or ( su sach tranh cai thuat toan khoa ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( su sach day kxy thuat ((o hoc) OR (co hoc)) ) OR ( su sach tranh cai thuat toan khoa )).
• Adding a wildcard symbol may retrieve word variants: (( su sach day kxy thuat ((o hoc) or (co hoc)) ) or ( su sach tranh cai thuat toan khoa ))*.