Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hieu van » hieu va, thien van, lieu va
thanh di » thanh doi, thanh de, thanh do
cham hoi » cham voi, cham h'roi, pham hoai
hoi gia » ho gia, hoc gia, hoa gia
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va
di cau » da cau, diem cau
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky nang ((x hoi) or (o hoi)). ((hieu ve) OR (hieu van)) cham hoi gia thanh di cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((x hoi) OR (o hoi)). ((hieu ve) OR (hieu van)) cham hoi gia thanh di cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((x hoi) or (o hoi)). ((hieu ve) OR (hieu van)) cham hoi gia thanh di cau tren".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((x hoi) or (o hoi)). ((hieu ve) OR (hieu van)) cham hoi gia thanh di cau tren*.