Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
hieu van » thien van, lieu va, hieu ve
su sach » so sach, vu sach
lam duc » lam duoc, pham duc, nam duoc
duc van » duc va, duc tan, duc manh
hieu va » lieu va, hieu qua
sach ty » sach y, sach tu, sach thu
nang ma » tang ma, sang ma, nang cao
ty nang » ky nang, ty xang, ty hang
ma hoi » mai hoi, xa hoi, ma hoa
va cua » va chua, via cua, ma cua
ca cua » co cua

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

• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty nang ma hoi. ((hieu van) OR (hieu va)) lam duc van hanh ((va cua) OR (ca cua)) vat~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty nang ma hoi. ((hieu van) or (hieu va)) lam duc van hanh ((va cua) OR (ca cua)) vat~".
• Adding a wildcard symbol may retrieve word variants: su sach ty nang ma hoi. ((hieu van) or (hieu va)) lam duc van hanh ((va cua) OR (ca cua)) vat*.