Perhaps you should try some spelling variations:
hanh dieu » han dieu, hinh dieu, hoang dieu
dieu tra » dieu tri, kiem tra, dieu cua
tang hoa » hang hoa, tang ha, tang ho
nam thuc » nam thuoc, nam thu, nam tu
tu sach » thu sach, te sach, tu cach
va hanh » van hanh, va thanh, va danh
hieu ve » hieu va, hieu van
hoa hoi » khoa hoi, hoa hoc, hoa doi
ky tang » ky nang, ky dang, kho tang
su sach » so sach, vu sach
tra tre » tran tren, tran tri, tran tro

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 (su sach)) ky tang hoa hoi. hieu ve ((nam thuc) OR (am thuc)) va hanh dieu tra tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky tang hoa hoi. hieu ve ((nam thuc) OR (am thuc)) va hanh dieu tra tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (su sach)) ky tang hoa hoi. hieu ve ((nam thuc) OR (am thuc)) va hanh dieu tra tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky tang hoa hoi. hieu ve ((nam thuc) OR (am thuc)) va hanh dieu tra tre*.