Francis Galton's breakfast study: https://psychclassics.yorku.ca/Galton/imagery.htm

The first official study where the term "aphantasia" was coined: https://psycnet.apa.org/record/2015-57165-051

David Marks - Original VVIQ: https://davidfmarks.com/2020/03/10/vividness-of-visual-imagery-questionnaire-vviq/