Skidmore, Lem (25 June 1979). "Nonapplications: Preparation Vital". Computerworld. 13 (26). IDG Enterprise: SR/2 and SR/28. ISSN 0010-4841. Retrieved 28 February 2021. https://books.google.com/books?id=Yg3gMg3D-H4C&pg=RA1-PA42
Mace, Scott (21 March 1988). "Pansophic Adds Plain English Query Language to Easytrieve". InfoWorld. 10 (12). InfoWorld Media Group, Inc.: 28. ISSN 0199-6649. https://books.google.com/books?id=9j4EAAAAMBAJ&pg=PA28
Piscopo, Joseph A. (2002-05-03). "Oral history interview with Joseph Piscopo": 16. hdl:11299/107601. {{cite journal}}: Cite journal requires |journal= (help) http://conservancy.umn.edu/handle/11299/107601
Piscopo, Joseph A. (2002-05-03). "Oral history interview with Joseph Piscopo": 16. hdl:11299/107601. {{cite journal}}: Cite journal requires |journal= (help) http://conservancy.umn.edu/handle/11299/107601
Bergin, Thomas J.; Haigh, Thomas (October 2009). "The Commercialization of Database Management Systems, 1969–1983". IEEE Annals of the History of Computing. 31 (4): 26–41. doi:10.1109/MAHC.2009.107. ISSN 1058-6180. S2CID 12367040. https://ieeexplore.ieee.org/document/5370777