Fix broken links (#578)

Fix broken links in operating_systems
Fix broken link in networks
Fix broken link in robotics (plus typo)
Fix Unikernel paper links

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)
 

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)

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)

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

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)