The examples are from the following side:
https://webdocs.cs.ualberta.ca/~games/PCP/list.htm
[1]Richard J. Lorentz, Creating difficult instances of the Post Correspondence Problem, CG 2000, 2000.
[2]http://www.informatik.uni-leipzig.de/~pcp/pcpcontest_en.html 

They have to be converted.
