Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
va trien » va truyen, va thiet, va tuyen
su sach » so sach, vu sach
co sach » bo sach, cuon sach, hoc sach
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
bac tuc » bac tu, bach tuoc, bac thua
va hanh » van hanh, va thanh, va danh
y nang » ky nang, ly nang, v nang
ma hoi » mai hoi, xa hoi, ma hoa
tuc va » thuc va, truc va, tuc xa
vi va » vi van, vai va, vu va

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