Perhaps you should try some spelling variations:
khanh trinh » hanh trinh, thanh trinh, nhanh tinh
trinh nhiet » trinh thiet, trinh nghien, trinh triet
trinh viet » ninh viet, trinh vat
trinh he » trinh han, trinh hoa, trinh thi
so hanh » so sanh, so danh, co hanh
tu hoc » te hoc
du hoc » duoc hoc
he du » te du, ve du

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: (( so hanh ((trinh nhiet) OR (trinh viet)) tu hoc ) OR ( duy khanh trinh he du hoc ))~.
• Adding a wildcard symbol may retrieve word variants: (( so hanh ((trinh nhiet) or (trinh viet)) tu hoc ) or ( duy khanh trinh he du hoc ))*.