> which is why it took 20 years of further research to go from Lisp 1 to Scheme.
Actually it only took Peter Landin a few years. For example see:
P. J. Landin, The Mechanical Evaluation of Expressions, The Computer Journal, Volume 6, Issue 4, January 1964, Pages 308–320, https://doi.org/10.1093/comjnl/6.4.308
