Magazine articles:

Waterloo's "30 Series", cover and pages 2-29, January-February 1999, Two-Cylinder Magazine

The John Deere Model "630" Tractor, cover and pages 2-21, May-June1995, Two-Cylinder Magazine

Books:

The John Deere 30 Series, Second Edition, by J.R. Hobbs, Green Magazine,1994

Brochures:

Step Up to new farming ease and convenience, B-453-58-8-Waterloo, 1958

Websites:

JohnnyPopper.com