Perhaps you should try some spelling variations:
va thuat » ky thuat, ki thuat, va thuc
thuat do » thuat o
cach tam » cach lam, cach ta, canh tam
tam than » ban than
so sanh » do sanh
sanh va » hanh va, anh va, sinh va
tu cach » tu cac
than vo » than va, than doc, than hoc
do khi » doi khi, do thi, co khi
vo thi » do thi, vu thi

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( so sanh va thuat do khi ) or ( tu cach tam than vo thi ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( so sanh va thuat do khi ) OR ( tu cach tam than vo thi )).
• Adding a wildcard symbol may retrieve word variants: (( so sanh va thuat do khi ) or ( tu cach tam than vo thi ))*.