Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hang hoi » hang hoa, hang hai, hang doi
ban hang » ngan hang
cham dua » chay dua, cham giua, pham duc
hoi cau » hoi chu, hoc cau, hoa cau
dua ban » dia ban, cua ban, qua ban
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va
dai hoi » dai hoc, dai hai, dai moi
mai hoi » mai khoi, lai hoi, mai doi

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) or (dai hoi)). ((hieu va) OR (hieu qua)) cham dua ban hang hoi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((mai hoi) OR (dai hoi)). ((hieu va) OR (hieu qua)) cham dua ban hang hoi cau tren*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((mai hoi) or (dai hoi)). ((hieu va) OR (hieu qua)) cham dua ban hang hoi cau tren*".