Perhaps you should try some spelling variations:
trinh nghien » trinh nghe, kinh nghiem, trinh thiet
sach trinh » sach tranh, hanh trinh, sach kinh
tra nghiem » trac nghiem, trai nghiem, thi nghiem
nghien su » nghiem su, nghien cuu, nghiep sua
khanh tra » thanh tra, khanh trach, khanh hoa
nghiem de » nghiem d, nghiem te, nghiem ve
su khanh » su thanh, vu khanh, su khang
su sach » so sach, vu sach
su hoc » tu hoc, du hoc, so hoc
de hoc » te hoc, du hoc, dien hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( su sach trinh nghien su hoc ) or ( su khanh tra nghiem de hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( su sach trinh nghien su hoc ) OR ( su khanh tra nghiem de hoc ))*.