Perhaps you should try some spelling variations:
vat hanh » vat thanh, van hanh, va hanh
hieu van » hieu va, thien van, lieu va
dang hoa » dang hoai, dang khoa, dong hoa
hanh ki » hanh vi, hanh ky, hanh kien
sach ky » sac ky, sach ty, sach kem
hieu ve » hieu va
su tien » su kien, su hien, tu tieng
hoa hoi » khoa hoi, hoa hoc, hoa doi
ki su » ky 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 ky) OR (sach y)) dang hoa hoi. ((hieu ve) or (hieu van)) am thuc vat hanh ki su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach y)) dang hoa hoi. ((hieu ve) OR (hieu van)) am thuc vat hanh ki su tien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sach y)) dang hoa hoi. ((hieu ve) or (hieu van)) am thuc vat hanh ki su tien".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sach y)) dang hoa hoi. ((hieu ve) or (hieu van)) am thuc vat hanh ki su tien*.