Download from mentors.debian.net?

[Torquil Macdonald Sørensen <torquil@gmail.com>]

Hi!

Could someone please point me to documentation that explains how to download 
source packages from mentors.debian.net?

I've tried adding:

deb-src http://mentors.debian.net/debian/ unstable main

to sources.list, but 'apt-get update' returns:

W: Failed to fetch 
bzip2:/var/lib/apt/lists/partial/mentors.debian.net_debian_dists_unstable_main_source_Sources 
 Encountered a section with no Package: header

E: Some index files failed to download. They have been ignored, or old ones used 
instead.

Strangly, I seem to not be able to find any such documentation. Am I overlooking 
something obvious? :-)

Thanks!
Torquil Sørensen