These come from:

https://osdn.net/projects/sfnet_jcamcalib/downloads/jcamcalib/0.7/chessboard-pattern.pdf/
https://osdn.net/frs/g_redir.php?m=kent&f=jcamcalib%2Fjcamcalib%2F0.7%2Fchessboard-pattern.pdf

When printing, use sturdy paper if you have it.
But do NOT use glossy paper: that would give undesirable reflections in 
white and black parts.