diff --git a/src/geometry/nearest_points.md b/src/geometry/nearest_points.md
index 4aab174d5..0c8abc259 100644
--- a/src/geometry/nearest_points.md
+++ b/src/geometry/nearest_points.md
@@ -173,6 +173,6 @@ In fact, to solve this problem, the algorithm remains the same: we divide the fi
 * [UVA 10245 "The Closest Pair Problem" [difficulty: low]](https://uva.onlinejudge.org/index.php?option=onlinejudge&page=show_problem&problem=1186)
 * [SPOJ #8725 CLOPPAIR "Closest Point Pair" [difficulty: low]](https://www.spoj.com/problems/CLOPPAIR/)
 * [CODEFORCES Team Olympiad Saratov - 2011 "Minimum amount" [difficulty: medium]](http://codeforces.com/contest/120/problem/J)
-* [Google CodeJam 2009 Final " Min Perimeter "[difficulty: medium]](https://code.google.com/codejam/contest/311101/dashboard#s=a&a=1)
+* [Google CodeJam 2009 Final "Min Perimeter" [difficulty: medium]](https://github.com/google/coding-competitions-archive/blob/main/codejam/2009/world_finals/min_perimeter/statement.pdf)
 * [SPOJ #7029 CLOSEST "Closest Triple" [difficulty: medium]](https://www.spoj.com/problems/CLOSEST/)
 * [TIMUS 1514 National Park [difficulty: medium]](https://acm.timus.ru/problem.aspx?space=1&num=1514)
diff --git a/src/geometry/planar.md b/src/geometry/planar.md
index 1c613f585..3fe667ab9 100644
--- a/src/geometry/planar.md
+++ b/src/geometry/planar.md
@@ -13,7 +13,7 @@ In this article we will deal with finding both inner and outer faces of a planar
 
 ## Some facts about planar graphs
 
-In this section we present several facts about planar graphs without proof. Readers who are interested in proofs should refer to [Graph Theory by R. Diestel](https://sites.math.washington.edu/~billey/classes/562.winter.2018/articles/GraphTheory.pdf) or some other book.
+In this section we present several facts about planar graphs without proof. Readers who are interested in proofs should refer to [Graph Theory by R. Diestel](https://diestel-graph-theory.com/) (see [video lectures](https://www.youtube.com/@DiestelGraphTheory) based on this book) or some other book.
 
 ### Euler's theorem
 Euler's theorem states that any correct embedding of a connected planar graph with $n$ vertices, $m$ edges and $f$ faces satisfies: