When using multiple sans-serif fonts in one document, it is necessary to know the internal name of a font to use it, as described here: How do I use a particular font for a small section of text in my document?
Unfortunately, I was not able to determine the internal name for the Source Sans Pro font (package: sourcesanspro). So my question is: what is the internal name for this font?
To be more precise:
I use pdflatex.
I would like to do something like:
\fontfamily{xyz}\selectfontwhere I need to know, what "xyz" would be.

Source Sans Pro, the name of the font files areSourceSansPro-Regular.ttf,SourceSansPro-Bold.ttf, &c. – Bernard Nov 04 '16 at 13:32