Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
nang mai » nang ma, nang tai, lang mai
mai khoi » mai khoa, tai khoa, cac khoi
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
dua tren » dung tren
tu sach » su sach, te sach, tu cach
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
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) OR (thu sach)) ky nang mai khoi. hieu va cac nuoc va hanh vi ((dua tren) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky nang mai khoi. hieu va cac nuoc va hanh vi ((dua tren) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) ky nang mai khoi. hieu va cac nuoc va hanh vi ((dua tren) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (thu sach)) ky nang mai khoi. hieu va cac nuoc va hanh vi ((dua tren) or (cuu tre))*.