apt-get error messages

[Klaus Jantzen <k.d.jantzen@mailbox.org>]

Hi,

due to a typing error - I wanted to say 'dpkg --add-architecture i386'
but wrote 'i368' -
I get the following error messages when running apt-get update:

<msgs>
...

W: Failed to fetch
http://download.virtualbox.org/virtualbox/debian/dists/vivid/Release 
Unable to find expected entry 'contrib/binary-i368/Packages' in Release
file (Wrong sources.list entry or malformed file)

W: Failed to fetch
http://ftp-stud.hs-esslingen.de/debian/dists/wheezy-updates/Release 
Unable to find expected entry 'main/binary-i368/Packages' in Release
file (Wrong sources.list entry or malformed file)

W: Failed to fetch
http://security.debian.org/dists/wheezy/updates/Release  Unable to find
expected entry 'main/binary-i368/Packages' in Release file (Wrong
sources.list entry or malformed file)

...
</msgs>

Where is the information for these erroneous requests stored?
How can I remove it?

Thanks for any hint. 
-- 

K.D.J.