Update listing for SICP book (EbookFoundation#7035)

The web.mit.edu URL returns a 404. Updated to most authoritative PDF source I could find. Also added author attributions to both SICP listings.

Author: NeilsC

books/free-programming-books-subjects.md

@@ -805,8 +805,8 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Programming Languages: Application and Interpretation (2nd Edition)](http://cs.brown.edu/~sk/Publications/Books/ProgLangs/) - Shriram Krishnamurthi
 * [Programming Languages: Theory and Practice](http://people.cs.uchicago.edu/~blume/classes/aut2008/proglang/text/offline.pdf) - Robert Harper (PDF)
 * [Semantics with Applications: A Formal Introduction](http://www.cs.ru.nl/~herman/onderwijs/semantics2019/wiley.pdf) - Hanne Riis Nielson, Flemming Nielson (PDF)
-* [Structure and Interpretation of Computer Programs](https://mitpress.mit.edu/sicp/)
-* [Structure and Interpretation of Computer Programs](http://sarabander.github.io/sicp/html/index.xhtml)
+* [Structure and Interpretation of Computer Programs](https://web.mit.edu/6.001/6.037/sicp.pdf) - Harold Abelson, Gerald Jay Sussman, Julie Sussman (PDF)
+* [Structure and Interpretation of Computer Programs](https://sarabander.github.io/sicp/html/index.xhtml) - Harold Abelson, Gerald Jay Sussman, Julie Sussman (HTML)
 * [The Black Art of Programming](http://self.gutenberg.org/wplbn0002828847-the-black-art-of-programming-by-mcilroy-mark.aspx?) - Mark McIlroy
 * [The Craft of Programming](https://kilthub.cmu.edu/articles/The_Craft_of_Programming/6610514) - John C. Reynolds
 * [Theory of Computation, Making Connections](https://joshua.smcvt.edu/computation) - Jim Hefferon (PDF)