Added more references and book cover graphics. (#490)

docs/courses/csintro/references.md

@@ -1,27 +1,54 @@
 # References
 
-![Stack of books](/static/courses/csintro/books.png)
 
-We have included some additional reference books and materials if you are interested in learning more about Maker Education, Physical Computing or Design Thinking in the classroom.
 
+We have included some additional reference books and materials if you are interested in learning more about the maker mindset.
+
+##Maker Education, Physical Computing or Design Thinking in the Classroom
+
+![Invent to Learn Book Cover](/static/courses/csintro/references/invent-to-learn.jpg)
 * [Invent To Learn](http://inventtolearn.com/)
 
->   Making, Tinkering, and Engineering in the Classroom By Sylvia Libow Martinez & Gary Stager
-	
+>   Making, Tinkering, and Engineering in the Classroom By Sylvia Libow Martinez and Gary Stager
+
+![Launch Book Cover](/static/courses/csintro/references/launch.jpg)	
 * [Launch](http://thelaunchcycle.com/)
 
 >	Using Design Thinking to Boost Creativity and Bring Out the Maker in Every Student by John Spencer and AJ Juliani
-	
+
+![Innovator's Mindset Book Cover](/static/courses/csintro/references/innovators-mindset.jpg)	
 * [The Innovator's Mindset](http://georgecouros.ca/blog/archives/5715)
 
->	Empower Learning, Unleash Talent, and Lead a Culture of Creativity
-by George Couros
-	
+>	Empower Learning, Unleash Talent, and Lead a Culture of Creativity by George Couros
+
+![Makerspace Projects Book Cover](/static/courses/csintro/references/makerspace-projects.jpg)	
 * [The Big Book of Makerspace Projects](https://colleengraves.org/bigmakerbook/)
 
 >   Inspiring Makers to Experiment, Create, and Learn by Colleen Graves
+
+##Code and Computational Thinking
+
+![Code Book Cover](/static/courses/csintro/references/code.jpg)	
+* [Code](http://www.charlespetzold.com/code/)
+
+>   The Hidden Language of Computer Hardware and Software by Charles Petzold
+
+![Girl Code Book Cover](/static/courses/csintro/references/girl-code.jpg)	
+* [Girl Code](https://www.girlcodethebook.com/)
+
+>   Gaming, Going Viral, and Getting it Done by Andy Gonzales and Sophie Houser
+
+![Secret Coders Book Cover](/static/courses/csintro/references/secret-coders.jpg)	
+* [Secret Coders](http://www.secret-coders.com/)
+
+>   Secret Coders by Gene Luen Yang and Mike Holmes
+
+![How to Count Book Cover](/static/courses/csintro/references/how-to-count.png)	
+* [How to Count](https://stevenf.com/books/)
+
+>   Programming for Mere Mortals, Vol. 1 by Steven Frank
 	
-If you have feedback for the Microsoft MakeCode team, you can fill our their survey form here: https://aka.ms/microbitfeedback
+If you have feedback for the Microsoft MakeCode team, you can fill out their survey form here: https://aka.ms/microbitfeedback
 
 The support site for the micro:bit is located here: [https://support.microbit.org](https://support.microbit.org/)