Write additional info about how .ins and .dtx files are built

ECS.bib

@@ -23,6 +23,12 @@
   title = {docstrip – Remove comments from file},
   url = {https://ctan.org/pkg/docstrip?lang=en}
 }
+@electronic{pack_write,
+  author = {Scott Pakin},
+  title = {Anintroduction to writing .ins and .dtx files},
+  year = {2008},
+  url = {https://www.tug.org/TUGboat/tb29-2/tb92pakin.pdf}
+}
 @electronic{latex_patels,
   author = {Sunil Patel and Velimir Gayevskiy},
   title = {Help Guide to the LaTeX template},

Rebuilding.tex

@@ -8,7 +8,7 @@ The templates are built using the docstrip package.
 "The pack­age pre­pares a \LaTeX  ker­nel or pack­age source file for ac­tual use, by re­mov­ing the doc­u­men­ta­tion and meta-data" \citep{Docstrip}
 It also creates a document containing some documentation for the created files.
 
-The docstrip utility comes as a latex package so when the main file (.dtx) is run with the command \verb|latex ecsdocs.dtx| it creates all the class files plus the example templates.
+The docstrip utility comes as a latex package so when the main file (.dtx) is run with the command \verb|$(LATEX) ecsdocs.ins| it creates all the class files plus the example templates.
 When this tool is run it creates lots of auxiliary files.
 To help with managing these auxiliary files GNU Make is used. "GNU Make is a tool which controls the generation of executables and other non-source files of a program from the program's source files."\citep{GNUdesc}.
 
@@ -16,6 +16,9 @@ The make command can be run in several different configurations. \verb|make all|
 
 \section{The Source File}
 The source file \verb|ecsdocs.dtx| results in the several different class (\verb|.cls|) files as well as the template (\verb|.tex|) files.
+"The installer is the \verb|ecsdocs.ins| file. An installer file
+extracts the code from a \verb|.dtx| file, uses \verb|DocStrip| to
+strip off the comments and documentation, and outputs the \verb|.cls| files."\citep{}
 It also creates the figure files and the chapter files.
 Whilst this creates a mess of files all in one folder the \verb|make install| command is designed to clean them up into a folder structure described in Listing~\ref{folder_struct}.
 The dtx file is designed to ensure continuity across different classes: names, font, department page styling and other formats.