Ancestry.com. R.L. Polk & Co.'s Duluth directory, 1917 [database on-line]. Provo, UT: The Generations Network, Inc., 2004.Original data: R.L. Polk & Co.'s Duluth directory, 1917 : embracing an alphabetical list of business firms and private citizens, a classified business directory and buyers guide, an up-to-date street directory, a miscellaneous directory of city and county officers, election districts, National Guard and conscription army, etc.. Duluth, Minn.: Duluth Directory Co., 1917.