Fix broken links in #3672 (#4700)

* Update mathematica links

Addresses #3672 for wolfram/mathematica link

* update sonatype eclipse book

* update mysql tutorial link

* update ravichaganti powershell book

* update single devops collective book

* fix mysql tutorial formatting

* reorder mysql 8.0 tutorial

* update leanpub requirements

* include devops collective author

free-programming-books.md

@@ -558,7 +558,6 @@
 * [Ordinary Differential Equations](https://en.wikibooks.org/wiki/Ordinary_Differential_Equations) - Wikibooks
 * [Plane Geometry (1913)](http://djm.cc/library/Plane_Geometry_Wentworth_Smith_edited.pdf) - George Wentworth and David Eugene Smith (PDF)
 * [Planes and Spherical Trigonometry (1915)](http://djm.cc/library/Plane_Spherical_Trigonometry_Wentworth_Smith_edited_2.pdf) - George Wentworth and David Eugene Smith (PDF)
-* [Power Programming with Mathematica](http://mathematica.stackexchange.com/questions/16485/are-you-interested-in-purchasing-david-wagners-power-programming-with-mathemat/22724) - David B. Wagner
 * [Probability and Statistics Cookbook](http://statistics.zone)
 * [Probability and Statistics EBook](http://wiki.stat.ucla.edu/socr/index.php/Probability_and_statistics_EBook)
 * [Recreations in Math](http://djm.cc/library/Recreations_in_Mathematics_Licks_edited.pdf) - H. E. Licks (PDF)
@@ -1979,9 +1978,10 @@ Kerridge (PDF) (email address *requested*, not required)
 ### Mathematica
 
 * [Mathematica® programming: an advanced introduction by Leonid Shifrin](http://www.mathprogramming-intro.org)
+* [Power Programming with Mathematica](http://mathematica.stackexchange.com/questions/16485/are-you-interested-in-purchasing-david-wagners-power-programming-with-mathemat/22724) - David B. Wagner
 * [Stephen Wolfram's The Mathematica Book](http://reference.wolfram.com/legacy/v5_2/)
 * [Vector Math for 3d Computer Graphics](http://chortle.ccsu.edu/VectorLessons/index.html)
-* [Wolfram Mathematica Tutorial Collection](http://www.wolfram.com/learningcenter/tutorialcollection/)
+* [Wolfram Mathematica Product Training: Wolfram U](https://www.wolfram.com/wolfram-u/catalog/product-training/mathematica/)
 
 
 ### MATLAB
@@ -2004,7 +2004,7 @@ Kerridge (PDF) (email address *requested*, not required)
 
 ### Maven
 
-* [Developing with Eclipse and Maven](http://books.sonatype.com/m2eclipse-book/reference/)
+* [Developing with Eclipse and Maven](https://books.sonatype.com/m2eclipse-book/reference/index.html)
 * [Maven by Example](http://books.sonatype.com/mvnex-book/reference/public-book.html)
 * [Maven: The Complete Reference](http://books.sonatype.com/mvnref-book/reference/public-book.html)
 * [Repository Management with Nexus](http://books.sonatype.com/nexus-book/reference/)
@@ -2029,8 +2029,8 @@ Kerridge (PDF) (email address *requested*, not required)
 
 ### MySQL
 
+* [MySQL 8.0 Tutorial Excerpt](https://dev.mysql.com/doc/mysql-tutorial-excerpt/8.0/en/tutorial.html) (HTML) [(PDF)](https://downloads.mysql.com/docs/mysql-tutorial-excerpt-8.0-en.pdf)
 * [MySQL Essentials](http://www.techotopia.com/index.php/MySQL_Essentials)
-* [MySQL Tutorial Excerpt](http://downloads.mysql.com/docs/mysql-tutorial-excerpt-5.5-en.pdf) (PDF)
 
 
 ### Neo4J
@@ -2233,7 +2233,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [DevOps: The Ops Perspective](https://www.gitbook.com/book/devopscollective/devops-the-ops-perspective/details) (PDF, ePub, MOBI)
 * [Ditch Excel: Making Historical & Trend Reports in PowerShell](https://www.gitbook.com/book/devopscollective/ditch-excel-making-historical-trend-reports-in-po/details) (PDF, ePub, MOBI)
 * [Introduction to PowerShell for Unix People](https://www.gitbook.com/book/devopscollective/a-unix-person-s-guide-to-powershell/details) (PDF, ePub, HTML)
-* [Layman’s Guide to PowerShell 2.0 remoting](http://www.ravichaganti.com//blog/wp-content/uploads/2010/12/A%20layman's%20guide%20to%20PowerShell%202.0%20remoting-v2.pdf) (PDF)
+* [Layman’s Guide to PowerShell 2.0 remoting](https://ravichaganti.com/ebooks/AlaymansguidetoPowerShell2remotingv2.pdf) (PDF)
 * [Learn PowerShell Core 6.0](https://www.packtpub.com/free-ebooks/learn-powershell-core-60) - David das Neves, Jan-Hendrik Peters (Packt account *required*)
 * [Learn PowerShell in Y Minutes](https://learnxinyminutes.com/docs/powershell/)
 * [Mastering PowerShell v2](http://community.idera.com/powershell/powertips/b/ebookv2#pi619PostSortOrder=Ascending)
@@ -2241,7 +2241,7 @@ Kerridge (PDF) (email address *requested*, not required)
 * [PowerShell Notes for Professionals](http://books.goalkicker.com/PowerShellBook/) - Compiled from StackOverflow documentation (3.x)
 * [PowerShell Succinctly, Syncfusion](https://www.syncfusion.com/resources/techportal/ebooks/powershell) (PDF, Kindle) (email address *requested*, not required)
 * [PowerShell Tips to Write By](https://leanpub.com/powershelltips) - Adam Bertram *(Leanpub account or valid email requested)* (:construction: *in process*)
-* [Secrets of PowerShell Remoting](https://www.gitbook.com/book/devopscollective/secrets-of-powershell-remoting/details) (PDF, ePub, MOBI)
+* [Secrets of PowerShell Remoting](https://leanpub.com/secretsofpowershellremoting) - The DevOps Collective, Inc. (PDF, ePub, MOBI, HTML) *(Leanpub account or valid email requested)*
 * [The Big Book of PowerShell Error Handling](https://www.gitbook.com/book/devopscollective/the-big-book-of-powershell-error-handling/details) (PDF, ePub, MOBI)
 * [The Big Book of PowerShell Gotchas](https://www.gitbook.com/book/devopscollective/the-big-book-of-powershell-gotchas/details) (PDF, ePub, MOBI)
 * [The Monad Manifesto - Annotated](https://www.gitbook.com/book/devopscollective/the-monad-manifesto-annotated/details) (PDF, ePub, MOBI)