backintime: Where are the sources from?

[c.buhtz at posteo.jp]

Dear "Little Girl",

thank you for your reply. But sorry, my question wasn't clear enough.

I wasn't looking for upstream maintainers or the upstream repo.

What I want to know is how can I be sure where the ubuntu package got 
its sources from. I assume it isn't upstream everytime!

For example backintime: Upstream is at GitHub. But there are also 
sources on Launchpad. That is what confuses me.

So I want to know on which sources the ubuntu package is based on.