- found: Salazar, V. Squares are not bad, 1967.
- found: NUCMC files (Rockwell, Harlow)
- found: Publishers weekly, 5/20/88 (Harlow Rockwell, 1910-1988, author and illustrator of children's books, d. 3/7/88)
- 1979-05-02: new
- 2009-02-20: revised