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

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) or (hoa hoc)). hieu van nam thuc dan 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) OR (hoa hoc)). hieu van nam thuc dan hanh dieu tra tre.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky tang ((hoa hoi) or (hoa hoc)). hieu van nam thuc dan hanh dieu tra tre*.