Perhaps you should try some spelling variations:
trinh nghien » trinh nghe, kinh nghiem, trinh thiet
chanh trinh » hanh trinh, thanh trinh, canh tranh
sach trinh » sach tranh, hanh trinh, sach kinh
tu chanh » tu hanh, tu thanh, tu chung
nghien d » nghiem d, nghien o, nghiem de
so sach » so sanh, bo sach, co sach
de hoc » te hoc, dien hoc
du hoc » tu hoc, duoc hoc
d hoc » ad hoc, y hoc, _ hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tu chanh trinh nghien ((de hoc) or (du hoc)) ) or ( so sach trinh nghien d hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu chanh trinh nghien ((de hoc) OR (du hoc)) ) OR ( so sach trinh nghien d hoc )).
• Adding a wildcard symbol may retrieve word variants: (( tu chanh trinh nghien ((de hoc) or (du hoc)) ) or ( so sach trinh nghien d hoc ))*.