Various enhancements

free-programming-books.md

@@ -470,7 +470,7 @@ Original Source: [List of freely available programming books](http://web.archive
 * [Linked Data Patterns: A pattern catalogue for modelling, publishing, and consuming Linked Data](http://patterns.dataincubator.org/book/) - Leigh Dodds, Ian Davis
 * [Magic Ink: Information Software and The Graphical Interface](http://worrydream.com/#!/MagicInk) - Bret Victor
 * [Mobile Developer's Guide to the Galaxy](https://leanpub.com/mobiledevelopersguide)
-* [Modeling Reactive Systems with Statecharts](http://www.scribd.com/doc/167971960/Modeling-Reactive-Systems-With-Statecharts)
+* [Modeling Reactive Systems with Statecharts](http://www.wisdom.weizmann.ac.il/~harel/reactive_systems.html)
 * [Mother Tongues of Computer Languages](http://www.digibarn.com/collections/posters/tongues/) (PNG)
 * [Networks, Crowds, and Markets: Reasoning About a Highly Connected World](http://www.cs.cornell.edu/home/kleinber/networks-book/)
 * [Object-Oriented Reengineering Patterns](http://win.ua.ac.be/~sdemey/) - Serge Demeyer, Stéphane Ducasse and Oscar Nierstrasz
@@ -549,7 +549,7 @@ Original Source: [List of freely available programming books](http://web.archive
 * [The Little Book of Semaphores](http://greenteapress.com/semaphores/) - Allen B. Downey
 * [Think OS: A Brief Introduction to Operating Systems](http://www.greenteapress.com/thinkos/index.html) - Allen B. Downey (PDF)
 * [UNIX Application and System Programming, lecture notes](http://www.compsci.hunter.cuny.edu/~sweiss/course_materials/unix_lecture_notes.php) - Prof. Stewart Weiss (PDF)
-* [Xv6, a simple Unix-like teaching operating system](http://pdos.csail.mit.edu/6.828/2012/xv6.html) (PDF)
+* [Xv6, a simple Unix-like teaching operating system](http://pdos.csail.mit.edu/6.828/2012/xv6.html)
 
 
 #### Parallel Programming
@@ -663,7 +663,7 @@ Original Source: [List of freely available programming books](http://web.archive
 * [Models of Computation](http://cs.brown.edu/people/jes/book/) - John E. Savage
 * [Network Science](http://barabasilab.neu.edu/networksciencebook/index.html)
 * [Practical Foundations for Programming Languages, Preview](http://www.cs.cmu.edu/~rwh/plbook/book.pdf) - Robert Harper (PDF)
-* [Principles of Programming Languages](http://www.cs.jhu.edu/~scott/pl/book/dist/) - Scott F. Smith
+* [Principles of Programming Languages](https://web.archive.org/web/20150418034451/http://www.cs.jhu.edu/~scott/pl/book/dist/) - Scott F. Smith
 * [Programming and Programming Languages](http://papl.cs.brown.edu/2014/index.html) - Shriram Krishnamurthi
 * [Programming in Martin-Löf's Type Theory](http://www.cse.chalmers.se/research/group/logic/book/) - Bengt Nordstroem
 * [Programming Languages: Application and Interpretation (2nd Edition)](http://www.cs.brown.edu/~sk/Publications/Books/ProgLangs/)
@@ -1551,7 +1551,7 @@ For resources on Angular, Backbone, D3, Dojo, Ember, Express, jQuery, Knockout,
 ### Parrot / Perl 6
 
 * [Perl 6 Programming](https://en.wikibooks.org/wiki/Perl_6_Programming)
-* [Using Perl 6](http://github.com/perl6/book/) (work in progress)
+* [Using Perl 6](https://github.com/perl6/book/) (work in progress)
 
 
 ### PC-BSD
@@ -1612,8 +1612,8 @@ For resources on Angular, Backbone, D3, Dojo, Ember, Express, jQuery, Knockout,
 
 ### PicoLisp
 
-* [PicoLisp by Example](http://www.scribd.com/doc/103733857/PicoLisp-by-Example)
-* [PicoLisp Works](http://www.scribd.com/doc/103732688/PicoLisp-Works)
+* [PicoLisp by Example](https://github.com/tj64/picolisp-by-example)
+* [PicoLisp Works](https://github.com/tj64/picolisp-works)
 
 
 ### PostgreSQL
@@ -1897,9 +1897,9 @@ For resources on Angular, Backbone, D3, Dojo, Ember, Express, jQuery, Knockout,
 * [A Scala Tutorial for Java programmers](http://www.scala-lang.org/docu/files/ScalaTutorial.pdf) (PDF)
 * [Another tour of Scala](http://naildrivin5.com/scalatour)
 * [EAI Patterns with Actor Model](https://github.com/alexanderfefelov/eai-patterns-with-actor-model) - Vaughn Vernon
-* [Effective Scala](http://twitter.github.com/effectivescala/)
+* [Effective Scala](https://twitter.github.com/effectivescala/)
 * [Learning Scalaz](http://eed3si9n.com/learning-scalaz/)
-* [Pro Scala: Monadic Design Patterns for the Web](http://github.com/leithaus/XTrace/tree/monadic/src/main/book/content/)
+* [Pro Scala: Monadic Design Patterns for the Web](https://github.com/leithaus/XTrace/tree/monadic/src/main/book/content/)
 * [Program Transformation in Scala](http://homepages.cwi.nl/~ai/MScThesis-A-Izmaylova.pdf) - Anastasia Izmaylova (PDF)
 * [Programming in Scala, First Edition](http://www.artima.com/pins1ed/)
 * [S-99: Ninety-Nine Scala Problems](http://aperiodic.net/phil/scala/s-99/) - Phil! Gold
@@ -1912,13 +1912,13 @@ For resources on Angular, Backbone, D3, Dojo, Ember, Express, jQuery, Knockout,
 * [Scala Tutorial](http://www.tutorialspoint.com/scala/scala_tutorial.pdf) (PDF)
 * [tetrix in Scala](http://eed3si9n.com/tetrix-in-scala-html5-book)
 * [The Neophyte's Guide to Scala](http://danielwestheide.com/scala/neophytes.html) - Daniel Westheide
-* [Xtrace](http://github.com/leithaus/XTrace/tree/monadic/src/main/book/content/)
+* [Xtrace](https://github.com/leithaus/XTrace/tree/monadic/src/main/book/content/)
 
 
 #### Lift
 
 * [Exploring Lift](http://exploring.liftweb.net) (published earlier as "The Definitive Guide to Lift", [PDF](http://groups.google.com/group/the-lift-book))
-* [Lift](http://github.com/tjweir/liftbook)
+* [Lift](https://github.com/tjweir/liftbook)
 * [Lift Cookbook](http://chimera.labs.oreilly.com/books/1234000000030/index.html) - Richard Dallaway
 * [Simply Lift](http://simply.liftweb.net/Simply_Lift.pdf) - David Pollak (PDF)
 
@@ -2076,7 +2076,7 @@ For resources on Angular, Backbone, D3, Dojo, Ember, Express, jQuery, Knockout,
 
 ### VHDL
 
-* [Free Range VHDL](http://github.com/fabriziotappero/Free-Range-VHDL-book) - Bryan Mealy, Fabrizio Tappero (TeX and PDF)
+* [Free Range VHDL](https://github.com/fabriziotappero/Free-Range-VHDL-book) - Bryan Mealy, Fabrizio Tappero (TeX and PDF)
 * [VHDL Tutorial](http://www.seas.upenn.edu/~ese171/vhdl/vhdl_primer.html)
 * [VHDL Tutorial](http://hep.uchicago.edu/~tangjian/SVT_sub/FTK_ATLAS/AUX/vhdl-tutorial.pdf) - Peter J. Ashenden (PDF)
 * [VHDL Tutorial: Learn By Example](http://esd.cs.ucr.edu/labs/tutorial/)