Documentation.md

@@ -61,7 +61,7 @@ For security reasons, you can't login with a combination of username and passwor
 - The first factor is given by the SSH public key. Please send your SSH _public_ key to the HPC team. You can find general information on public key authentication [here](https://www.ssh.com/academy/ssh/public-key-authentication).
 - The second factor involves the Cisco Duo app. To use it, you will need to enroll your account, see [cisco-duo-setup.pdf](uploads/cd518a29f4362a9383c7345a975ed065/cisco-duo-setup.pdf) .
 
-If you own a [Yubikey](https://en.wikipedia.org/wiki/YubiKey) hardware token, you can also use it (in [OTP[(https://en.wikipedia.org/wiki/One-time_password) mode) as the second authentication factor instead of Cisco Duo. If you are interested in using a Yubikey, please contact the [HPC-Team](mailto:hpc-mgr@uni-koeln.de). Please note: we can't provide Yubikeys to users, but it could be a worthwhile investment for about 50€.
+If you own a [Yubikey](https://en.wikipedia.org/wiki/YubiKey) hardware token, you can also use it (in [OTP](https://en.wikipedia.org/wiki/One-time_password) mode) as the second authentication factor instead of Cisco Duo. If you are interested in using a Yubikey, please contact the [HPC-Team](mailto:hpc-mgr@uni-koeln.de). Please note: we can't provide Yubikeys to users, but it could be a worthwhile investment for about 50€.
 
 After you have successfully enrolled in Duo and prepared your SSH Key, please send your key.