Perhaps you should try some spelling variations:
trinh cong » trinh dung
hanh trinh » canh tranh, hanh chinh
sach tren » sach tien, sach tranh
tren cong » trien cong, tien cong, tran cong
cong khi » cong thai, khong khi, co khi
te sach » toc sach
tu hanh » du hanh, lu hanh, thuc hanh

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( te sach tren cong khi đong luc ) or ( tu hanh trinh cong khi đong luc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( te sach tren cong khi đong luc ) OR ( tu hanh trinh cong khi đong luc )).
• Adding a wildcard symbol may retrieve word variants: (( te sach tren cong khi đong luc ) or ( tu hanh trinh cong khi đong luc ))*.