Nietzsche's Ubermensch: Concept & Theory
https://study.com/academy/lesson/nietzsches-bermensch-concept-theory.html
An overview of the notion of the "Superman" that gives the play its title and is alluded to in Act III.
George Bernard Shaw - Biographical
https://www.nobelprize.org/prizes/literature/1925/shaw/biographical/
An overview of Shaw's biography on the Nobel Prize site (Shaw won the Nobel Prize for literature in 1925).
Don Juan
https://www.gutenberg.org/files/21700/21700-h/21700-h.htm
Lord Byron's poem about Don Juan, the mythical libertine who appears in Act III and is ostensibly an ancestor of Jack Tanner's.