Perhaps you should try some spelling variations:
nam duoc » nam thuoc, da duoc, dat duoc
cua viet » ca viet, hoa viet, cua vat
ban hanh » ban hang
hieu van » hieu va, thien van, lieu va
lam duoc » luat duoc, lam thuoc, tao duoc
tu sach » thu sach, su sach, te sach
cuu tre » cua tre, cau tren, cau treo
sach ky » sac ky, sach y, sach ty
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang

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 ky tang xa hoi. hieu van ((lam duoc) OR (nam duoc)) ban hanh vi ((cua viet) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky tang xa hoi. hieu van ((lam duoc) OR (nam duoc)) ban hanh vi ((cua viet) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky tang xa hoi. hieu van ((lam duoc) OR (nam duoc)) ban hanh vi ((cua viet) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky tang xa hoi. hieu van ((lam duoc) OR (nam duoc)) ban hanh vi ((cua viet) or (cuu tre))*.