Added reference to Bitcoin Fundamentals review appendix

03_how_ln_works.asciidoc

@@ -10,6 +10,19 @@ If you have experience in computer science, cryptography, Bitcoin, and protocol
 If you are less experienced, this chapter shall give you a good enough overview so you will have an easier time understanding the formal protocol specifications, known as BOLTs (Basis of Lightning Technology).
 In case you are a beginner, this chapter will help you better understand the technical chapters of the book.
 
+If you need a refresher on the fundamentals of Bitcoin, you can find a summary review of the following topics in <<bitcoin_fundamentals_review>>:
+
+* Keys and addresses
+* Hash functions
+* Digital signatures
+* Transaction structure
+* Transaction inputs and outputs
+* Transaction chaining
+* Bitcoin script
+* Multsignature addresses and scripts
+* Timelocks
+* Complex scripts
+
 We'll start with a one sentence definition of what the Lightning Network (LN) is and break it down in the remainder of this chapter.
 
 **The Lightning Network (LN) is a peer-to-peer network of _payment channels_ implemented as smart contracts on the _Bitcoin blockchain_ as well as a communication protocol that defines how participants set up and execute these smart contracts**