Perhaps you should try some spelling variations:
nang mai » nang ma, lang mai, nang cai
nang tai » hang tai, tang tai, sang tai
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
dua tren » dung tren
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky

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

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