This article chronicling a day of activity in the city before the mayoral primary included a snippet at Wayne State 's Walter P. Reuther Library. \"I need something on the Purple Gang,\" Ceil Jensen tells Tom Featherstone, an archivist in the audiovisual collection of the Reuther. Jensen of Rochester Hills is assembling a photo book on Detroit \'s Polish community. Like scholars and researchers from around the world each month, she comes to the nation\'s most important repository of documents about the American labor movement. Featherstone\'s department alone has about 2 million photos, 10,000 videotapes, 10,000 sound recordings and 2,500 films.