Perhaps you should try some spelling variations:
dang khoa » dung khoa, hang khoa, dang khoi
hieu van » hieu va, thien van, lieu va
vat hanh » vat thanh, van hanh, va hanh
sach thu » sach thue, sach thieu, sach tham
khoa hoi » khoan hoi, khoa hoc, khoa doi
hanh ki » hanh vi, hanh ky, hanh kien
hieu ve » hieu va
sach ty » sach y, sach tu, xach tay
su hien » su kien, su tien, thu hien
ki su » ky su

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 ty) OR (sach thu)) dang khoa hoi. ((hieu ve) or (hieu van)) am thuc vat hanh ki su hien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach thu)) dang khoa hoi. ((hieu ve) OR (hieu van)) am thuc vat hanh ki su hien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ty) OR (sach thu)) dang khoa hoi. ((hieu ve) or (hieu van)) am thuc vat hanh ki su hien".
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) OR (sach thu)) dang khoa hoi. ((hieu ve) or (hieu van)) am thuc vat hanh ki su hien*.