Book: Barlow, Raymond E. & Kaiser, Joan E. 1999 The Glass Industry in Sandwich. 5.
• Similar "ring" jar but with colorless rings: no. 5121; mentioned is the Cape Cod Glass Company whose "List of Glass Ware" lists "Blown Ring Jars and Covers... with flint or blue rings"Article: Spillman, Jane Shadel. 06//2013 Gillinder & Sons Glassware: A Catalogue (part 2). Glass Club Bulletin of the National American Glass Club. (223): 5-19.
• Gillander & Sons (Philadelphia) Glass catalogue showing 5 drawings of ring jars: p. 6 (top), jars from one quart to two gallons. Probably 1880s. (See also Bulliten no. 222 for part 1 of series.)