Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
hieu van » thien van, lieu va, hieu ve
tu sach » thu sach, su sach, te sach
danh vi » hanh vi, dinh vi, danh di
va danh » va dinh, va dan, va hanh
nam xuc » cam xuc, nam xua, nam duoc
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
ma hoi » mai hoi, xa hoi, ma hoa
vi cua » vai cua, di cua

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 y nang ma hoi. ((hieu van) or (hieu va)) ((nam xuc) OR (nam thuc)) va danh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ma hoi. ((hieu van) OR (hieu va)) ((nam xuc) OR (nam thuc)) va danh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang ma hoi. ((hieu van) or (hieu va)) ((nam xuc) OR (nam thuc)) va danh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ma hoi. ((hieu van) or (hieu va)) ((nam xuc) OR (nam thuc)) va danh vi cua tre*.