Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hieu cac » hieu luc, hieu va, hieu van
danh dai » danh dau, danh di, danh sai
hieu cao » chieu cao, hieu ca, kieu cao
tap trac » tap toan
dai cau » dat cau, da cau, dai hau
va danh » va dinh, va dan, va hanh
trac va » truc va, tac va, thac va
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
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: tu sach ky nang ((x hoi) or (o hoi)). ((hieu cao) or (hieu cac)) tap trac va danh dai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((x hoi) OR (o hoi)). ((hieu cao) OR (hieu cac)) tap trac va danh dai cau tren.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((x hoi) or (o hoi)). ((hieu cao) or (hieu cac)) tap trac va danh dai cau tren*.