edit to preface

book.tex

@@ -160,12 +160,12 @@ didn't do a quantitative study to support this claim.)
 It is now 2016 and I too have returned to teach at Indiana University.
 In my absence the compiler course had switched from the front-to-back
 organization to a back-to-front organization. Seeing how well the
-incremental approach worked at Colorado, I found this rather
-unsatisfactory and have proceeded to reorganize the course, porting
-and adapting the structure of the Colorado course back into the land
-of Scheme. Of course, in the meantime Scheme has been superseded by
-Racket (at least in Indiana), so the course is now about implementing,
-in Racket~\citep{plt-tr}, a subset of Racket.
+incremental approach worked at Colorado, I found this unsatisfactory
+and have reorganized the course, porting and adapting the structure of
+the Colorado course back into the land of Scheme. In the meantime
+Scheme has been superseded by Racket (at least in Indiana), so the
+course is now about compiling a subset of Racket to the x86 assembly
+language and the compiler is implemented in Racket~\citep{plt-tr}.
 
 This is the textbook for the incremental version of the compiler
 course at Indiana University (Spring 2016) and it is the first