* [An Introduction to Scheme and its Implementation](ftp://ftp.cs.utexas.edu/pub/garbage/cs345/schintro-v14/schintro_toc.html)
* [An Introduction to Scheme and its Implementation](http://www.cs.rpi.edu/academics/courses/fall00/ai/scheme/reference/schintro-v14/schintro_toc.html)
* [Concrete Abstractions: An Introduction to Computer Science Using Scheme](https://gustavus.edu/+max/concrete-abstractions.html)
* [Concrete Abstractions: An Introduction to Computer Science Using Scheme](https://gustavus.edu/+max/concrete-abstractions.html)