https://www.gamesdatabase.org/game/commodore-64/ultima-iv-quest-of-the-avatar
https://www.gamesdatabase.org/Media/SYSTEM/Atari_ST/manual/Formated/Ultima_IV-_Quest_of_the_Avatar_-_1987_-_ORIGIN_Systems.pdf
https://www.c64-wiki.com/wiki/Ultima_IV_%E2%80%93_Quest_of_the_Avatar#Design
http://www.zzap64.co.uk/cgi-bin/displaypage.pl?issue=13&page=67
