diff --git a/distributed_systems/README.md b/distributed_systems/README.md
index 90e07fc..6ffb0b4 100644
--- a/distributed_systems/README.md
+++ b/distributed_systems/README.md
@@ -63,7 +63,7 @@
 
 * [Unicorn: A System for Searching the Social Graph](http://db.disi.unitn.eu/pages/VLDBProgram/pdf/industry/p871-curtiss.pdf)
 
-* [Unikernels: Library Operating Systems for the Cloud](http://anil.recoil.org/papers/2013-asplos-mirage.pdf)
+* [Unikernels: Library Operating Systems for the Cloud](http://unikernel.org/files/2013-asplos-mirage.pdf)
 
 * [Untraceable Electronic Mail, Return Addresses, and Digital Pseudonyms](http://www.cs.utexas.edu/~shmat/courses/cs395t_fall04/chaum81.pdf)
 
diff --git a/networks/README.md b/networks/README.md
index 8a743a3..16aefaf 100644
--- a/networks/README.md
+++ b/networks/README.md
@@ -2,6 +2,6 @@
 
 * [Bimodal Multicast](http://www.csl.mtu.edu/cs6461/www/Reading/Birman99.pdf)
 * [End-to-End Arguments in System Design](http://www.deepplum.com/dpr/locus/Papers/EndtoEnd.html)
-* [Can SPDY Really Make the Web Faster?](http://www.comp.lancs.ac.uk/~elkhatib//Docs/2014.06_Netw.pdf)
+* [Can SPDY Really Make the Web Faster?](http://www.eecs.qmul.ac.uk/~tysong/files/IFIPNetworking14.pdf)
 * [Datacenter Traffic Control: Understanding Techniques and Trade-offs](https://osf.io/6qzxc/)
 * [B4: Experience with a Globally-Deployed Software Defined WAN](https://dl.acm.org/citation.cfm?id=2486019)
diff --git a/operating_systems/README.md b/operating_systems/README.md
index 4793c4e..b7da84b 100644
--- a/operating_systems/README.md
+++ b/operating_systems/README.md
@@ -8,7 +8,6 @@
 
 ## Jails and containers
 
-* :scroll: [Jails: Confining the omnipotent root.](https://us-east.manta.joyent.com/bcantrill/public/ppwl-cantrill-jails.pdf)
-
-* :scroll: [Solaris Zones: Operating System Support for Consolidating Commercial Workloads](https://us-east.manta.joyent.com/bcantrill/public/ppwl-cantrill-zones.pdf)
+* :scroll: [Jails: Confining the omnipotent root.](http://phk.freebsd.dk/pubs/sane2000-jail.pdf)
 
+* :scroll: [Solaris Zones: Operating System Support for Consolidating Commercial Workloads](https://www.usenix.org/legacy/event/lisa04/tech/full_papers/price/price.pdf)
diff --git a/robotics/README.md b/robotics/README.md
index cfdc0cd..2221fe5 100644
--- a/robotics/README.md
+++ b/robotics/README.md
@@ -9,7 +9,7 @@ Robotics
 
 [Online Trajectory Generation: Basic Concepts for Instantaneous Reactions to Unforeseen Events](http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=5350749)
 
-[Probablistic Roadmaps for Path Planning in High-Dimensional Configuration Spaces](http://www.kavrakilab.org/sites/default/files/kavraki1996prm-high-dim-conf.pdf)
+[Probablistic Roadmaps for Path Planning in High-Dimensional Configuration Spaces](https://www.cs.cmu.edu/~./motionplanning/papers/sbp_papers/PRM/prmbasic_01.pdf)
 
 [Rapidly-Exploring Random Trees: A New Tool for Path Planning](http://msl.cs.uiuc.edu/~lavalle/papers/Lav98c.pdf)
 
@@ -29,7 +29,7 @@ planning. The problem of motion planning scales exponentially with the
 degrees of freedom a robot has and the degrees of freedom the obstacles
 in an environment have. Thus, planning with high degrees of freedom leads to many problems
 such as incompleteness and extremely slow speed. The PRM method was the first to
-propose a sampling-based stratey to deal with motion planning and
+propose a sampling-based strategy to deal with motion planning and
 created a practical method for offline planning of robot manipulators.
 The RRT method modified PRM by using a tree structure rather than a
 graph so that non-holonomic and other constraints could be considered
diff --git a/unikernels/README.md b/unikernels/README.md
index ab053eb..43311f9 100644
--- a/unikernels/README.md
+++ b/unikernels/README.md
@@ -27,7 +27,7 @@
 
 ### Introduction
 
-* [Unikernels: Library Operating Systems for the Cloud](http://anil.recoil.org/papers/2013-asplos-mirage.pdf)
+* [Unikernels: Library Operating Systems for the Cloud](http://unikernel.org/files/2013-asplos-mirage.pdf)
 * [Unikernels: the rise of the virtual library operating system](https://cacm.acm.org/magazines/2014/1/170866-unikernels/fulltext)
 * [Maximizing hypervisor scalability using minimal virtual machines](https://core.ac.uk/download/pdf/35074556.pdf)
 * [Breaking up is hard to do: security and functionality in a commodity hypervisor](https://open.library.ubc.ca/media/download/pdf/24/1.0052016/1)