fix gray locks link

README.md

@@ -119,7 +119,7 @@ See the [sources](#sources) and [selection criteria](#selection-criteria) below.
 1. **A Relational Model of Data for Large Shared Data Banks. [Codd (1970)](https://www.seas.upenn.edu/~zives/03f/cis550/codd.pdf).**
     \
     <sub>Databases</sub>
-    * Granularity of Locks and Degrees of Consistency in a Shared Data Base. [Gray et al (1975)](http://web.eecs.umich.edu/~jag/eecs584/papers/lock-granularity.pdf).
+    * Granularity of Locks and Degrees of Consistency in a Shared Data Base. [Gray et al (1975)](https://www.cs.cmu.edu/~natassa/courses/15-721/papers/GrayLocks.pdf).
     * Access Path Selection in a Relational Database Management System. [Selinger et al (1979)](https://courses.cs.duke.edu/compsci516/cps216/spring03/papers/selinger-etal-1979.pdf).
     * The Transaction Concept: Virtues and Limitations. [Gray (1981)](https://jimgray.azurewebsites.net/papers/theTransactionConcept.pdf).
     * The design of POSTGRES. [Stonebraker, Rowe (1986)](https://dl.acm.org/doi/pdf/10.1145/16856.16888).
@@ -298,7 +298,7 @@ See the [sources](#sources) and [selection criteria](#selection-criteria) below.
 1. **A Protocol for Packet Network Intercommunication. [Cerf, Kahn (1974)](https://www.cs.princeton.edu/courses/archive/fall06/cos561/papers/cerf74.pdf).**
 1. Self-stabilizing systems in spite of distributed control. [Dijkstra (1974)](https://dl.acm.org/doi/pdf/10.1145/361179.361202).
 1. The Mythical Man Month. [Brooks (1975)](https://www.cs.virginia.edu/~evans/greatworks/mythical.pdf).
-1. Granularity of Locks and Degrees of Consistency in a Shared Data Base. [Gray et al (1975)](http://web.eecs.umich.edu/~jag/eecs584/papers/lock-granularity.pdf).
+1. Granularity of Locks and Degrees of Consistency in a Shared Data Base. [Gray et al (1975)](https://www.cs.cmu.edu/~natassa/courses/15-721/papers/GrayLocks.pdf).
 1. The Semantics of Predicate Logic as a Programming Language. [Van Emden, Kowalski (1976)](https://dl.acm.org/doi/pdf/10.1145/321978.321991).
 1. **New Directions in Cryptography. [Diffie, Hellman (1976)](https://ee.stanford.edu/~hellman/publications/24.pdf).**
 1. A Universal Algorithm for Sequential Data Compression. [Ziv, Lempel (1977)](https://courses.cs.duke.edu/spring03/cps296.5/papers/ziv_lempel_1977_universal_algorithm.pdf).

papers.yml

@@ -341,7 +341,7 @@
     - title: Granularity of Locks and Degrees of Consistency in a Shared Data Base
       author: Gray et al
       year: 1975
-      link: http://web.eecs.umich.edu/~jag/eecs584/papers/lock-granularity.pdf
+      link: https://www.cs.cmu.edu/~natassa/courses/15-721/papers/GrayLocks.pdf
     - title: "The Transaction Concept: Virtues and Limitations"
       author: Gray
       year: 1981