"Lost Sheep", review, Variety (New York, N.Y.), May 7, 1930, p. 70, col. 3-4. Internet Archive, San Francisco, California. Retrieved September 27, 2018.
"Sidney Fox", obituary, Variety, November 18, 1942, p. 54, col. 2. Internet Archive. Retrieved September 26, 2018.
"The Fifteenth Census of the United States: 1930", Bureau of the Census, U.S. Department of Commerce; digital copy of original enumeration page including Sidney "Liefer" Fox's family, New York City, April 3, 1930. FamilySearch, archives of The Church of Jesus Christ of Latter-day Saints, Salt Lake City, Utah. Retrieved September 26, 2018.
The earlier "United States Census of 1920" documents Joseph and Rose Fox living with their children and step-children in Passaic, New Jersey, with 13-year-old Sidney listed as Sadie in that federal population schedule.
"Sidney Fox". Internet Broadway Database. The Broadway League. Archived from the original on July 24, 2018. Retrieved July 24, 2018.
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"WAMPAS Baby Stars of 1931 with Ernestine Schumann-Heink", video of the 1931 WAMPAS Baby Stars; originally posted April 9, 2011, by "Furn738" on YouTube, Alphabet, Inc., Mountain View, California. Sidney Fox is the second young woman introduced in this ceremony. Retrieved September 27, 2018.