Perhaps you should try some spelling variations:
dang hoa » dang hoai, dang khoa, dong hoa
vat hanh » vat thanh, van hanh, va hanh
hieu van » hieu va, thien van, lieu va
hieu ve » hieu va
hoa hoi » khoa hoi, hoa hoc, hoa doi
tu sach » thu sach, su sach, tu cach
ky dang » ky nang, ky danh
te sach » toc sach
su tien » su kien, su hien, tu tieng
vi su » va su, ve su, ki su
thuc » thu

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) OR (te sach)) ky dang hoa hoi. ((hieu ve) or (hieu van)) am thuc vat hanh vi su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (te sach)) ky dang hoa hoi. ((hieu ve) OR (hieu van)) am thuc vat hanh vi su tien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (te sach)) ky dang hoa hoi. ((hieu ve) or (hieu van)) am thuc vat hanh vi su tien".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (te sach)) ky dang hoa hoi. ((hieu ve) or (hieu van)) am thuc vat hanh vi su tien*.