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