Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
dua ngan » dung ngan, luat ngan, cua nganh
cua ngan » cua ban, vu ngan, cua dan
hang vai » hang va, hang tai, hang hai
cac tren » ca tren, cau tren, rac tren
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va, hieu qua
vai cac » va cac, tai cac, voi cac
va nam » van nam, ha nam, va nay

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky nang ((mai hoi) or (ma hoa)). hieu va nam ((dua ngan) OR (cua ngan)) hang vai cac tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang ((mai hoi) OR (ma hoa)). hieu va nam ((dua ngan) OR (cua ngan)) hang vai cac tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky nang ((mai hoi) or (ma hoa)). hieu va nam ((dua ngan) OR (cua ngan)) hang vai cac tren".
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang ((mai hoi) or (ma hoa)). hieu va nam ((dua ngan) OR (cua ngan)) hang vai cac tren*.