Perhaps you should try some spelling variations:
sang mai » sang ma, sang tai, lang mai
nam thuc » nam thuoc, nam thu, nam tu
vu sach » vu bach, su sach, vu khach
sach ky » sac ky, sach y, sach ty
ky sang » ky nang, ky dang, ky tang
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
ca viet » va viet, hoa viet, san viet
co viet » so viet, o viet, hoc viet

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ky sang mai hoi. hieu va ((nam thuc) OR (am thuc)) va hanh vi ((ca viet) or (co viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky sang mai hoi. hieu va ((nam thuc) OR (am thuc)) va hanh vi ((ca viet) OR (co viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach ky sang mai hoi. hieu va ((nam thuc) OR (am thuc)) va hanh vi ((ca viet) or (co viet))".
• Adding a wildcard symbol may retrieve word variants: vu sach ky sang mai hoi. hieu va ((nam thuc) OR (am thuc)) va hanh vi ((ca viet) or (co viet))*.