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