Damström, Annika (16 February 1998). "Joonas Kolkan uudeksi seuraksi PSV Eindhoven" [The new company of Joonas Kolka is PSV Eindhoven]. Helsingin Sanomat (in Finnish). Retrieved 19 May 2022.
palloliitto.fi
"Kolkka Joonas" (in Finnish). palloliitto.fi. Archived from the original on 20 March 2012. Retrieved 16 March 2012.
"Kolkka Joonas" (in Finnish). Suomen Palloliitto (Football Association of Finland). Archived from the original on 14 August 2011. Retrieved 20 August 2011.
"Kolkka Joonas" (in Finnish). palloliitto.fi. Archived from the original on 20 March 2012. Retrieved 16 March 2012.
"Kolkka Joonas" (in Finnish). Suomen Palloliitto (Football Association of Finland). Archived from the original on 14 August 2011. Retrieved 20 August 2011.