rescue 2 links, add UNIX For Beginners

Author: avindra

src/courses.md

@@ -15,7 +15,8 @@ Origin of jschauma course is not certain. It may be even older
   * Institution: `Cornell University`
 * 2003: [COMS 214: Advanced Unix Tools](http://www.cs.cornell.edu/courses/cs214/2004sp/)
   * Institution: `Cornell University`
-* 2003: [Unix: An Oral History](http://www.princeton.edu/~hos/frs122/unixhist/oralhistory.htm)
+* 2003: [Unix: An Oral History](https://dspinellis.github.io/oral-history-of-unix/)
+  <!-- dead: http://www.princeton.edu/~hos/frs122/unixhist/oralhistory.htm -->
   * Institution: `Princeton University`
   * comprised mostly of writings and essays
 * 2006: [CS631APUE - Advanced Programming in the UNIX Environment](https://stevens.netmeister.org/631/)
@@ -26,4 +27,4 @@ Origin of jschauma course is not certain. It may be even older
 ## Alternative courses
 
  * 2001: [Unix Classes](http://boris.lk.net/unix/)
-   * by [Boris Veytsman](http://boris.lk.net/) for [itt](https://www.itt.com/)
+   * by [Boris Veytsman](http://boris.lk.net/) for [itt](https://www.itt.com/)

src/lang/shell.md

@@ -9,7 +9,8 @@ Shell languages often mix structured programming constructs with bespoke command
   * [view converted Markdown on GitHub](https://github.com/susam/tucl/blob/master/the-unix-command-language.md#the-unix-command-language)
   * The syntax (` | `) was [contributed by Douglas McIlroy](https://www.tuhs.org/pipermail/tuhs/2020-December/022535.html).
   * The original syntax can be found in 1987's [A Research UNIX Reader](https://archive.org/details/a_research_unix_reader/page/n27/mode/2up).
-* 1976: [Using a Command Language as a High-Level Programming Language](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.85.7617&rep=rep1&type=pdf)
+* 1976: [Using a Command Language as a High-Level Programming Language](https://grosskurth.ca/bib/1976/mashey-command.pdf) ([doi](https://dl.acm.org/doi/abs/10.5555/800253.807670))
+  <!-- dead: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.85.7617&rep=rep1&type=pdf -->
   * by John Mashey
 * 1978: [The UNIX Shell](https://archive.org/details/bstj57-6-1971/mode/2up) ([html](https://becksteinlab.physics.asu.edu/pages/unix/shell.html)) ([mirror](https://www.tuhs.org/Archive/Documentation/Papers/BSTJ/bstj57-6-1971.pdf))
   * by [Stephen Richard Bourne](https://dl.acm.org/profile/81100584611)

src/prim/man.md

@@ -19,3 +19,5 @@ Much information about Unix is available through it's manuals. The manuals are s
 * 1982: [Introduction to the UNIX Operating System](http://www.bitsavers.org/pdf/uNIX/uNIX_Jan82.pdf)
   * by [Stephen M. Walters](http://www.starrynights.us/Biography/Biography.htm)
   * A mix of notes, standard man pages and assembly code
+* 1997: [UNIX For Beginners (2e)](https://people.computing.clemson.edu/~dhouse/courses/405/docs/unix4beg.pdf) ([alternate format](https://wolfram.schneider.org/bsd/7thEdManVol2/beginners/beginners.pdf)) ([HTML to PDF dump](https://www.ualberta.ca/computing-science/media-library/docs/unix-beginners.pdf))
+  * by Brian Kernighan