Add some more footnotes

diff --git a/md/environment.md b/md/environment.md
index e1d0529eb8393123c17dcfc7046069277cd0cc64..0dcbb1e72e0d4b50a3f0ae364eba05f519167fa0 100644 (file)
--- a/md/environment.md
+++ b/md/environment.md
@@ -25,16 +25,20 @@ before downloading or redistributing.
 
 # Introduction
 
-The Muddle language is described in "The Muddle Programming Language",
-but in addition to the language itself, there is a rich and varied
-collection of software written in the language which facilitates the
-writing of programs and systems of programs in Muddle. The information
-describing this programming environment has been contained in various
-documents, some out of print or out of date, and in supplemental disk
-files describing changes and additions. Some of the packages of
-functions used to deal with Muddle code have never been formally
-documented. This manual brings together some of that scattered
-documentation.
+The Muddle language is described in "The Muddle Programming Language"
+[^2], but in addition to the language itself, there is a rich and
+varied collection of software written in the language which
+facilitates the writing of programs and systems of programs in Muddle.
+The information describing this programming environment has been
+contained in various documents, some out of print or out of date, and
+in supplemental disk files describing changes and additions. Some of
+the packages of functions used to deal with Muddle code have never
+been formally documented. This manual brings together some of that
+scattered documentation.
+
+[^2]: S. W. Galley and Greg Pfister.
+      *The Muddle Programming Language*.
+      MIT Laboratory for Computer Science, 1979.
 
 The document's purpose is to flesh out the description of the language
 contained in "The Muddle Programming Language", giving a fuller
@@ -453,8 +457,17 @@ or debugging systems, to more sophisticated aids such as `DEBUGR` and
 debugging.
 
 It should be noted that, in addition to the editors discussed below,
-RMODE and EMACS, TECO based text editors, understand much of the
-syntax and many of the conventions of Muddle programs.
+RMODE [^3] and EMACS [^4], TECO based text editors, understand much of
+the syntax and many of the conventions of Muddle programs.
+
+[^3]: P. David Lebling, R. V. Baron and Bruce K. Daniels.
+     *RMODE: A Real-time Edit Facility*.
+     Technical Report SYS.04.07-1, MIT LCS Programming Technology
+Division, October 1977.
+
+[^4]: Richard M. Stallman.
+     *EMACS*.
+     Technical Report 519, MIT AI Laboratory, August, 1979.
 
 ## 3.1. Pretty-Printing