+* (Another good book covering the same ground as the Hankin book, but
+more thoroughly, and in a more mathematical style, is *Lambda-Calculus and Combinators:
+an Introduction*, by J. Roger Hindley and Jonathan P. Seldin, currently $52 on [Amazon](http://www.amazon.com/dp/0521898854). If you choose to read
+both the Hankin book and this book, you'll notice the authors made some different
+terminological/notational choices. At first, this makes comprehension slightly slower,
+but in the long run it's helpful because it makes the arbitrariness of those choices more salient.)
+
+* (Another good book, covering some of the same ground as the previous two, but also delving much deeper into typed lambda calculi, is *Types and Programming Languages*, by Benjamin Pierce, currently $61 on [Amazon](http://www.amazon.com/dp/0262162091). This book has many examples in OCaml.)
+
+* *The Little Schemer, Fourth Edition*, by Daniel P. Friedman and Matthias
+Felleisen, currently $23 on [Amazon](http://www.amazon.com/exec/obidos/ASIN/0262560992).
+This is a classic text introducing the gentle art of programming, using the
+functional programming language Scheme. Many people love this book, but it has
+an unusual dialog format that is not to everybody's taste. **Of particular
+interest for this course** is the explanation of the Y combinator, available as
+a free sample chapter [at the MIT Press web page for the
+book](http://www.ccs.neu.edu/home/matthias/BTLS/).
+
+* *The Seasoned Schemer*, also by Daniel P. Friedman and Matthias Felleisen, currently $28
+on [Amazon](http://www.amazon.com/Seasoned-Schemer-Daniel-P-Friedman/dp/026256100X)
+
+* *The Little MLer*, by Matthias Felleisen and Daniel P. Friedman, currently $27
+on [Amazon](http://www.amazon.com/Little-MLer-Matthias-Felleisen/dp/026256114X).
+This covers some of the same introductory ground as The Little Schemer, but
+this time in ML. It uses another dialect of ML (called SML), instead of OCaml, but there are only
+superficial syntactic differences between these languages. [Here's a translation
+manual between them](http://www.mpi-sws.org/~rossberg/sml-vs-ocaml.html).