Perhaps you should try some spelling variations:
dieu cua » dieu tra
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
nam thuc » nam thuoc, am thuc, nam thu
su sach » vu sach
hieu va » lieu va, hieu qua
tu nano » truc nano
so sach » so sanh, bo sach, co sach
nano x » nano 1, nano o
va nam » van nam, ha nam, va nay
vi cua » vai cua, di cua
x hoi » xa hoi, o hoi, x ho

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sach) OR (so sach)) tu nano x hoi. hieu va nam thuc van hanh ((vi cua) or (dieu cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sach)) tu nano x hoi. hieu va nam thuc van hanh ((vi cua) OR (dieu cua)) tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) OR (so sach)) tu nano x hoi. hieu va nam thuc van hanh ((vi cua) or (dieu cua)) tre*".