Update Good DB papers.md

Author: heathersherry

topics/Good DB papers.md

@@ -38,5 +38,6 @@ __Others__
 1. NP Optimization Problems [[Link]](https://www8.cs.umu.se/kurser/TDBAfl/VT06/algorithms/COMPEND/COMPED19/COMPENDI.HTM)
 > * Greedy Set-Cover Algorithms [[Paper](https://www.cs.ucr.edu/~neal/Young08SetCover.pdf)]
 3. FAST-PPR: Personalized PageRank Estimation for Large Graphs [[Slides](https://cs.stanford.edu/people/plofgren/Fast-PPR_KDD_Talk.pdf)]
-4. Graph Theory [[PDF](http://math.tut.fi/~ruohonen/GT_English.pdf)]
-5. Graph Theory [[PDF](https://www.zib.de/groetschel/teaching/WS1314/BondyMurtyGTWA.pdf)]
+4. Graph Theory 1 [[PDF](https://www.maths.ed.ac.uk/~v1ranick/papers/wilsongraph.pdf)] 
+5. Graph Theory 2 [[PDF](https://www.zib.de/groetschel/teaching/WS1314/BondyMurtyGTWA.pdf)]
+6. Graph Theory 3 [[PDF](https://www2.math.ethz.ch/education/bachelor/lectures/fs2016/math/graph_theory/graph_theory_notes.pdf)]