Perhaps you should try some spelling variations:
trinh nghien » trinh nghe, kinh nghiem, trinh thiet
sanh trinh » hanh trinh, anh trinh, sinh trinh
nghien sua » nghiep sua, nghien cuu, nghiep vua
sanh trac » anh trac, sinh trac, canh tac
nghiem do » nghiem d, nghiem de, nghiem duoc
so sanh » do sanh
sua hoc » cua hoc, su hoc, sua khoa
do hoc » co hoc, do hoa, du hoc

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "(( so sanh trinh nghien sua hoc ) OR ( so sanh trac nghiem do hoc ))~".
• Adding a wildcard symbol may retrieve word variants: (( so sanh trinh nghien sua hoc ) OR ( so sanh trac nghiem do hoc ))*.