Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nang mai » nang tai, lang mai, nang cai
dua tren » dung tren
cap nuoc » dat nuoc
va hanh » van hanh, va thanh, va danh
van cap » van cau, van dap, van ca
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
cuu tre » cua tre, cau tren, 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) or (nang ma)) hoi. hieu van cap nuoc va hanh vi ((dua tren) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang mai) OR (nang ma)) hoi. hieu van cap nuoc va hanh vi ((dua tren) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang mai) or (nang ma)) hoi. hieu van cap nuoc va hanh vi ((dua tren) or (cuu tre))*.