Perhaps you should try some spelling variations:
nang mai » nang ma, nang tai, lang mai
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
dua tren » dung tren
cau tren » cu tren, dau tren, ca tren
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
cuu tre » cua tre, cau treo

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 nang mai hoi. hieu va cac nuoc va hanh vi ((dua tren) or (((cuu tre) OR (cau tren))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang mai hoi. hieu va cac nuoc va hanh vi ((dua tren) OR (((cuu tre) OR (cau tren)))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang mai hoi. hieu va cac nuoc va hanh vi ((dua tren) or (((cuu tre) OR (cau tren))))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang mai hoi. hieu va cac nuoc va hanh vi ((dua tren) or (((cuu tre) OR (cau tren))))*.