Perhaps you should try some spelling variations:
sach ngan » sach ngon, sach nha, sach han
ngan khoa » nganh khoa, nhan khoa, nhuan khoa
sanh anh » anh anh, thanh anh, doanh anh
khoa khi » khoa kham, khong khi, khoa khoa
so sach » so sanh, bo sach, co sach
anh so » anh son, anh co
so khi » co khi, so ki, bo khi

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( do sanh anh so khi đong luc ) or ( so sach ngan khoa khi đong luc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( do sanh anh so khi đong luc ) OR ( so sach ngan khoa khi đong luc )).
• Adding a wildcard symbol may retrieve word variants: (( do sanh anh so khi đong luc ) or ( so sach ngan khoa khi đong luc ))*.