Perhaps you should try some spelling variations:
hieu sach » chieu sach, dien sach, hieu cac
hieu cach » hieu cac, chieu sach, hieu ca
anh quang » anh xquang, anh quan, nhanh quang
tran hung » tran hong, tran hoang, tran huu
cong tap » cuong tap, cong tac, cong tan
tap toan » tap doan, tap quan, bai toan
toan cao » toan ban, toan tap

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

• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sach) OR (hieu cach)) - anh quang ((tran hung) OR (tran quang)) cong tap toan cao~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu sach) OR (hieu cach)) - anh quang ((tran hung) or (tran quang)) cong tap toan cao~".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sach) OR (hieu cach)) - anh quang ((tran hung) or (tran quang)) cong tap toan cao*.