Perhaps you should try some spelling variations:
trinh nghien » trinh nghe, kinh nghiem, trinh thiet
tranh nghien » tron nghien, trong nghien, truong nghien
canh trinh » canh tranh, hanh trinh, canh tinh
sach tranh » canh tranh
tu canh » thu canh, tu chanh, tu can
so sach » so sanh, bo sach, co sach
de hoc » te hoc, dien hoc
du hoc » tu hoc, duoc hoc
d hoc » y hoc, _ hoc, o 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 canh trinh nghien ((de hoc) or (du hoc)) ) or ( so sach tranh nghien ((d hoc) or (ad hoc)) ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu canh trinh nghien ((de hoc) OR (du hoc)) ) OR ( so sach tranh nghien ((d hoc) OR (ad hoc)) )).
• Adding a wildcard symbol may retrieve word variants: (( tu canh trinh nghien ((de hoc) or (du hoc)) ) or ( so sach tranh nghien ((d hoc) or (ad hoc)) ))*.