"Revanche nemen op het Lisp" (in Dutch). ohl.be. 10 February 2018. Archived from the original on 29 June 2018. Retrieved 29 June 2018. "Pearson puzzel" (in Dutch). ohl.be. 16 February 2018. Archived from the original on 29 June 2018. Retrieved 29 June 2018.
"Revanche nemen op het Lisp" (in Dutch). ohl.be. 10 February 2018. Archived from the original on 29 June 2018. Retrieved 29 June 2018. "Pearson puzzel" (in Dutch). ohl.be. 16 February 2018. Archived from the original on 29 June 2018. Retrieved 29 June 2018.