The exclusive purpose of these bibliographical notes is to aid further research. I shall neither list nor repeat any of the titles of the books and articles cited or quoted in the main text, except when I refer to some of them in the following pages, the main matter of which concerns archives and so-called primary sources. A further limitation: this book consists of descriptions of Philadelphia around 1900 and around 1950, as well as of seven biographical chapters: it is emphatically not a compendium of the history of the city during the first half of the twentieth century.