Perhaps you should try some spelling variations:
trinh nghien » trinh nghe, kinh nghiem, trinh thiet
thu nghiem » thuc nghiem, thi nghiem
sach trinh » sach tranh, hanh trinh, sach kinh
nghien tu » nghiep tu, nghien cuu, nghiep vu
sach thu » sach thue, sach thieu, sach tham
toc sach » hoc sach, doc sach, thuoc sach
su sach » so sach, vu sach
du hoc » duoc hoc
tu hoc » te hoc

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: (( su sach thu nghiem ((du hoc) OR (dai hoc)) ) OR ( toc sach trinh nghien tu hoc ))~.
• Adding a wildcard symbol may retrieve word variants: (( su sach thu nghiem ((du hoc) or (dai hoc)) ) or ( toc sach trinh nghien tu hoc ))*.