Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
tham thuc » nham thuc, tam thuc, thai thuc
hieu van » hieu va, thien van, hieu ve
nang ma » tang ma, sang ma, nang cao
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
tu bai » tu ban, tu bat, te bai
bai ky » ban ky, sai ky, bac ky
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 bai ky nang ma hoi. ((hieu van) OR (lieu va)) ((tham thuc) or (pham thuc)) va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu bai ky nang ma hoi. ((hieu van) OR (lieu va)) ((tham thuc) OR (pham thuc)) va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu bai ky nang ma hoi. ((hieu van) OR (lieu va)) ((tham thuc) or (pham thuc)) va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu bai ky nang ma hoi. ((hieu van) OR (lieu va)) ((tham thuc) or (pham thuc)) va hanh vi cua tre*.