'Fork' from the oiginal MetaMath Verifier in C# by Chris Capel.
As described on http://us.metamath.org/other.html:
Verifier.cs (29-Oct-2010) - a Metamath proof verifier (written in 550 lines of C# by Chris Capel). External link: verifier.cs [retrieved 3-Aug-2016]
I copied the code and split it up in seperate files.
Original code: http://us.metamath.org/downloads/Verifier.cs