404. That’s an error.
The requested URL /_/+1/confirm?hl=en&url=https://isach.net/sach-lam-viec-nhom/&name=6+cu%E1%BB%91n+s%C3%A1ch+gi%C3%BAp+b%E1%BA%A1n+n%C3%A2ng+cao+k%E1%BB%B9+n%C4%83ng+l%C3%A0m+vi%E1%BB%87c+nh%C3%B3m
was not found on this server. That’s all we know.