Perhaps you should try some spelling variations:
nang mai » nang ma, nang tai, lang mai
tu sach » thu sach, su sach, te sach
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » hieu qua
va danh » va dinh, va hanh, dia danh
cuu tre » cua tre, cau tren, cau treo
y nang » ky nang, ly nang, v nang
cac tu » cac thu, cach tu, cac du
va dan » ca dan, va dao, va dau
ca cuu » cap cuu, cua cuu, ca 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 sach y nang mai hoi. ((hieu va) or (lieu va)) cac tu ((va danh) OR (va dan)) ca cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang mai hoi. ((hieu va) OR (lieu va)) cac tu ((va danh) OR (va dan)) ca cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang mai hoi. ((hieu va) or (lieu va)) cac tu ((va danh) OR (va dan)) ca cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang mai hoi. ((hieu va) or (lieu va)) cac tu ((va danh) OR (va dan)) ca cuu tre*.