The Optional Memorial of Pope St. John XXIII is October 11.

Vatican source for his writings and speeches: http://w2.vatican.va/content/john-xxiii/en.html

Vatican biography http://w2.vatican.va/content/john-xxiii/en.html. or http://www.vatican.va/news_services/liturgy/saints/ns_lit_doc_20000903_john-xxiii_en.html

Franciscan Media https://www.franciscanmedia.org/saint-john-xxiii/

https://carfleo.com/2014/05/21/i-would-be-called-john-video-on-st-john-xxiii/