Perhaps you should try some spelling variations:
trach nhiem » trac nghiem
sanh trach » khanh trach, canh tranh, sach tranh
can trach » can tranh, canh tranh, can khach
so sanh » do sanh
nhiem d » nghiem d, nghiem de, nhiem va
tu can » tu ban, tu cac, thu canh
de hoc » te hoc, du hoc, dien hoc
tu hoc » te hoc
d hoc » du hoc, ad hoc, y hoc

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu can trach nhiem ((de hoc) OR (tu hoc)) ) OR ( so sanh trach nhiem d hoc ))~.
• Adding a wildcard symbol may retrieve word variants: (( tu can trach nhiem ((de hoc) or (tu hoc)) ) or ( so sanh trach nhiem d hoc ))*.