Perhaps you should try some spelling variations:
nang mai » nang ma, nang tai, lang mai
cau tren » cu tren, dau tren, ca tren
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
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 cau » cua cau, cac cau, can cau

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 cau tren~.
• 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 cau tren.
• 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 cau tren*.