Perhaps you should try some spelling variations:
thanh dieu » thanh lieu, than dieu, hanh dieu
dieu tra » dieu tri, kiem tra, dieu cua
va thanh » gia thanh, ban thanh, va tinh
nam thuc » nam thuoc, am thuc, nam thu
tu sach » thu sach, te sach, tu cach
thuc va » thuc vat, thuc dan, thuc day
hieu ve » hieu va, hieu van
hoa hoi » khoa hoi, hoa hoc, hoa doi
ky dang » ky nang, ky danh
ky tang » ky nang, kho tang, ky trong
su sach » so sach, vu sach
tra tre » tran tren, tran tri, tran tro
ve nam » he nam, va nam, le nam

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