diff --git a/sections/0-preface.md b/sections/0-preface.md
index 7b1f3d1..27841c8 100644
--- a/sections/0-preface.md
+++ b/sections/0-preface.md
@@ -1,6 +1,6 @@
## 0. Preface
-
+
What follows is a list of best practices I compiled for my colleagues,
advice sprung from the painful experience coming naturally from
diff --git a/sections/1-hygienic-rules.md b/sections/1-hygienic-rules.md
index 95807b9..eb679d5 100644
--- a/sections/1-hygienic-rules.md
+++ b/sections/1-hygienic-rules.md
@@ -1,6 +1,6 @@
## 1. Hygienic Rules
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+
These are general purpose hygienic rules that transcend the language
or platform rules. Programming language is a form of communication,
diff --git a/sections/2-language-rules.md b/sections/2-language-rules.md
index 714c678..128e30d 100644
--- a/sections/2-language-rules.md
+++ b/sections/2-language-rules.md
@@ -1,6 +1,6 @@
## 2. Language Rules
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+
### 2.1. MUST NOT use "return"
@@ -25,7 +25,7 @@ def action = Action { request =>
In Scala, a `return` statement inside a nested anonymous function is
implemented by throwing and catching a `NonLocalReturnException`. It
says so in the
-[Scala Language Specification, section 6.20](http://www.scala-lang.org/docu/files/ScalaReference.pdf).
+[Scala Language Specification, section 6.20](https://scala-lang.org/files/archive/spec/2.13/spec.pdf).
Besides, `return` is anti structural programming, as functions can be
described with multiple exit points and if you need `return`, like in
diff --git a/sections/3-architecture.md b/sections/3-architecture.md
index 3bc767e..9987c7b 100644
--- a/sections/3-architecture.md
+++ b/sections/3-architecture.md
@@ -1,6 +1,6 @@
## 3. Application Architecture
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+
### 3.1. SHOULD NOT use the Cake Pattern
diff --git a/sections/4-concurrency-parallelism.md b/sections/4-concurrency-parallelism.md
index 7ff20b8..d2fdeed 100644
--- a/sections/4-concurrency-parallelism.md
+++ b/sections/4-concurrency-parallelism.md
@@ -1,6 +1,6 @@
## 4. Concurrency and Parallelism
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+
### 4.1. SHOULD avoid concurrency like the plague it is
diff --git a/sections/5-actors.md b/sections/5-actors.md
index 2308599..968f870 100644
--- a/sections/5-actors.md
+++ b/sections/5-actors.md
@@ -1,6 +1,6 @@
## 5. Akka Actors
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+
### 5.1. SHOULD evolve the state of actors only in response to messages received from the outside