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
tang hoa » hang hoa, tang ho, nang hoa
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, te sach, tu cach
thuc va » thuc vat, thuc dan, thuc day
tang ha » lang ha, tang ma, trung ha
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) OR (tang ha)) hoi. hieu van 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 hoa) OR (tang ha)) hoi. hieu van 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 hoa) OR (tang ha)) hoi. hieu van nam thuc va thanh dieu tra tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky ((tang hoa) OR (tang ha)) hoi. hieu van nam thuc va thanh dieu tra tre*.