Anecdote about Joe Martin in this book, Rex Ingram: Hollywood's Rebel of the Silver Screen repeats Baby Peggy's version but offers another version of Joe's tragic end.
1920 feature in Popular Science features animal trainers and their stage ready creatures. This article shows not only an image of Curly Stecker, but also of Joe Martin as an orangutan and the infamous Charlie the elephant who would later cause the death of Curly Stecker.
Emma-Lindsay Squier's article "Joe Martin, Gentleman" gives an inside look at animal training and Joe's behavior onset. A notoriously difficult creature to work with Joe is shown in this article to be of great intellect and compassion.