Perhaps you should try some spelling variations:
trinh nghien » trinh nghe, kinh nghiem, trinh thiet
hanh trinh » canh tranh, hanh chinh
nghiem de » nghiem d, nghiem do, nghiem te
luoc hanh » luoc canh, luoc danh, quoc hanh
sach tai » sach bai, sach tham, sach xa
sach dao » lanh dao
de hoc » te hoc, du hoc, dien 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: (( te ((sach tai) OR (sach dao)) nghiem de hoc ) OR ( luoc hanh trinh nghien _ hoc ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( te ((sach tai) OR (sach dao)) nghiem de hoc ) or ( luoc hanh trinh nghien _ hoc ))~".
• Adding a wildcard symbol may retrieve word variants: (( te ((sach tai) OR (sach dao)) nghiem de hoc ) or ( luoc hanh trinh nghien _ hoc ))*.