Perhaps you should try some spelling variations:
manh nhanh » danh nhan, anh nhan, danh thanh
toan cau » toan cao, toan ban, toan tap
thai cau » thai cao, thai van, thai va
duc manh » suc manh, duc anh, duc minh
cac duc » cac du, cao duc, cac dac
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
ve cac » va cac, vien cac
o lai » o lao
o hoi » co hoi, o hoc, o hai

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 ((o hoi) or (o lai)). hieu ve cac duc manh nhanh ((thai cau) OR (toan cau)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (o lai)). hieu ve cac duc manh nhanh ((thai cau) OR (toan cau)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hoi) or (o lai)). hieu ve cac duc manh nhanh ((thai cau) OR (toan cau)) tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) or (o lai)). hieu ve cac duc manh nhanh ((thai cau) OR (toan cau)) tren*.