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