Perhaps you should try some spelling variations:
sach tranh » canh tranh
khoa kham » kho khan, khoa than
sach dao » lanh dao
khoa khi » khong khi, khoa khoa, khoa khac
te sach » toc sach
so sach » so sanh, bo sach, co sach
dao ha » dao hai, dao nha, dam ha
ha thi » pham thi

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 dao ha thi đong luc ) or ( so sach tranh ((khoa khi) OR (khoa kham)) đong luc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( te sach dao ha thi đong luc ) OR ( so sach tranh ((khoa khi) OR (khoa kham)) đong luc ))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( te sach dao ha thi đong luc ) or ( so sach tranh ((khoa khi) OR (khoa kham)) đong luc ))*".