diff --git a/.github/workflows/lychee.yml b/.github/workflows/lychee.yml
index ddc0fa6..9c79300 100644
--- a/.github/workflows/lychee.yml
+++ b/.github/workflows/lychee.yml
@@ -17,7 +17,7 @@ jobs:
       #env:
       #  GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
       with:
-        args: '--verbose --no-progress **/*.md'
+        args: '--verbose --max-retries 4 --no-progress **/*.md'
 
     - name: Create Issue From File
       uses: peter-evans/create-issue-from-file@v2
diff --git a/audio_comp_sci/README.md b/audio_comp_sci/README.md
index dccc56f..fe2e807 100644
--- a/audio_comp_sci/README.md
+++ b/audio_comp_sci/README.md
@@ -5,7 +5,7 @@
 * :scroll: [An Industrial-Strength Audio Search Algorithm](shazam-audio-search-algorithm.pdf) by Avery Li-Chun Wang
 
 * [WaveNet: A Generative Model for Raw Audio](https://arxiv.org/pdf/1609.03499.pdf) by a team @ Google DeepMind, 2016
-    * [Announcement and interactive examples](https://deepmind.com/blog/wavenet-generative-model-raw-audio/)
+    * [Announcement and interactive examples](https://www.deepmind.com/blog/wavenet-a-generative-model-for-raw-audio)
     * [[Python] Implementation with the Keras Neural Networks library](https://github.com/basveeling/wavenet)
     * [[Python] Implementation with the TensorFlow Machine Intelligence library](https://github.com/ibab/tensorflow-wavenet)
 
diff --git a/garbage_collection/README.md b/garbage_collection/README.md
index 5183aab..b8a5543 100644
--- a/garbage_collection/README.md
+++ b/garbage_collection/README.md
@@ -1,4 +1,4 @@
-* [A Unified Theory of Garbage Collection](https://researcher.watson.ibm.com/researcher/files/us-bacon/Bacon04Unified.pdf)
+* [A Unified Theory of Garbage Collection](https://www.cs.cornell.edu/courses/cs6120/2019fa/blog/unified-theory-gc/)
     > An overview for programmers and language implementors for understanding different garbage collection algorithms.
 * [A LISP Garbage-Collector for Virtual-Memory Computer Systems](https://www.cs.purdue.edu/homes/hosking/690M/p611-fenichel.pdf)
 
diff --git a/memory_management/README.md b/memory_management/README.md
index c1ef78a..95d75c7 100644
--- a/memory_management/README.md
+++ b/memory_management/README.md
@@ -1,18 +1,18 @@
 ## Memory Management
 
-* [A Unified Theory of Garbage Collection](https://researcher.watson.ibm.com/researcher/files/us-bacon/Bacon04Unified.pdf)
+* [A Unified Theory of Garbage Collection](https://web.eecs.umich.edu/~weimerw/2012-4610/reading/bacon-garbage.pdf)
 
 * [Teaching Garbage Collection without Implementing Compilers or Interpreters](https://cs.brown.edu/~sk/Publications/Papers/Published/cgkmf-teach-gc/paper.pdf)
 
 * [Message Analysis Guided Allocation and Low Pause Incremental GC in a Concurrent Language](http://user.it.uu.se/~kostis/Papers/ismm04.pdf)
 
-* [And Then There Were None: A Stall-Free Real-Time Garbage Collector for Reconfigurable Hardware](http://researcher.watson.ibm.com/researcher/files/us-bacon/Bacon12AndThen.pdf)
+* [And Then There Were None: A Stall-Free Real-Time Garbage Collector for Reconfigurable Hardware](https://cacm.acm.org/magazines/2013/12/169948-and-then-there-were-none/fulltext)
 
 * [The Slab Allocator: An Object-Caching Kernel Memory Allocator](https://www.usenix.org/legacy/publications/library/proceedings/bos94/bonwick.html)
   - [ASCII version](https://www.usenix.org/legacy/publications/library/proceedings/bos94/full_papers/bonwick.a)
   - [POSTSCRIPT version](https://www.usenix.org/legacy/publications/library/proceedings/bos94/full_papers/bonwick.ps)
 
-* :scroll: [ScatterAlloc: Massively Parallel Dynamic Memory Allocation for the GPU](http://www.icg.tugraz.at/Members/steinber/scatteralloc-1)
+* :scroll: [ScatterAlloc: Massively Parallel Dynamic Memory Allocation for the GPU](https://markussteinberger.net/papers/ScatterAlloc.pdf)
 
   Presents a useful algorithm as well as considerations relevant to designing algorithms for GPUs.
 
diff --git a/security/README.md b/security/README.md
index 326df66..68c111e 100644
--- a/security/README.md
+++ b/security/README.md
@@ -6,7 +6,7 @@
 * [Making Programs Forget: Enforcing Lifetime For Sensitive Data (2011)](https://www.usenix.org/events/hotos11/tech/final_files/Kannan.pdf)
 * [Breach: Reviving The Crime Attack (2013)](http://breachattack.com/resources/BREACH%20-%20SSL,%20gone%20in%2030%20seconds.pdf)
 * [Why Silent Updates Boost Security (2009)](http://tik-old.ee.ethz.ch/file/ef72343372ca8659a9ae8a98873167c0/TIKReport302.pdf)
-* [A survey of coordinated attacks and collaborative intrusion detection (2010)](https://www.tk.informatik.tu-darmstadt.de/fileadmin/user_upload/Group_TK/zhou2010survey.pdf)
+* [A survey of coordinated attacks and collaborative intrusion detection (2010)](https://www.sciencedirect.com/science/article/pii/S016740480900073X)
 
 * :scroll: [Macaroons: Cookies with Contextual Caveats for Decentralized Authorization in the Cloud (2014)](macaroons-cookies-with-contextual-caveats.pdf)
 * :scroll: [Insertion, Evasion, and Denial of Service: eluding network intrusion detection (1998)](ids-evasion-ptacek-newsham.pdf)