Perhaps you should try some spelling variations:
sach ngan » sach ngon, sach nha, sach han
ngan cong » nganh cong, nganh nong, ngan hang
sach tran » sach tranh, vach tran, sach tham
sach tren » sach tien, sach tranh
khoa khoa » hoa khoa, khuan khoa, khoa hoc
cong khi » cong thai, khong khi, co khi
su sach » so sach, vu sach

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 ngan cong khi đong luc ) or ( thu ((sach tran) OR (sach tren)) khoa khoa đong luc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( su sach ngan cong khi đong luc ) OR ( thu ((sach tran) OR (sach tren)) khoa khoa đong luc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( su sach ngan cong khi đong luc ) or ( thu ((sach tran) OR (sach tren)) khoa khoa đong luc ))".
• Adding a wildcard symbol may retrieve word variants: (( su sach ngan cong khi đong luc ) or ( thu ((sach tran) OR (sach tren)) khoa khoa đong luc ))*.