Perhaps you should try some spelling variations:
tren nghien » tron nghien, trinh nghien, trien nghiep
hanh trinh » canh tranh, hanh chinh
trinh nghe » trinh nghien, trinh he, trinh nha
sach tren » sach tien, sach tranh
nghien tu » nghiep tu, nghien cuu, nghiep vu
nghe dau » nghe dan, nghiem dau, nghiep dau
tu sach » thu sach, su sach, te sach
lu hanh » luu hanh, du hanh, ly hanh
dau hoc » dai hoc, du hoc, dan hoc
tu hoc » te 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 sach tren nghien tu hoc ) or ( lu hanh trinh nghe dau hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach tren nghien tu hoc ) OR ( lu hanh trinh nghe dau hoc )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach tren nghien tu hoc ) or ( lu hanh trinh nghe dau hoc ))*.