How can I find the source code that was used to build a certain nuget package

How can I find the source code that was used to build a certain nuget package, e.g. OxyPlot core library (PCL) 1.0.0-unstable210?

I just used the date now? I saw that the nuget package was published on april 11th 2016, so I was looking at the branches. The was no change on the master branch at this date, so I assume the develop-branch was used. There were 2 commits on april 11th. Can I figure out which one was used to build the nuget package?

Is there a better way or any kind of link between the nuget package and the source code version?

Best Regards

Bernd