diff --git a/TangDou/Topic/【换根】dfs专题.md b/TangDou/Topic/【换根】dfs专题.md
index fd7e4cc..49adc01 100644
--- a/TangDou/Topic/【换根】dfs专题.md
+++ b/TangDou/Topic/【换根】dfs专题.md
@@ -708,16 +708,22 @@ $$g[v][k] += (g[u][k - 1] - f[v][k - 2])$$
 注意数组下表不要越界。$g[i][j]$的初始值应该赋为$f[i][j]$，因为根节点的$g[i][j]$就是$f[i][j]$。（第二次$dfs$已知父亲节点推儿子节点）
 
 
+#### [$P6419$ $Kamp$](https://www.luogu.com.cn/problem/P6419)
+https://www.cnblogs.com/Troverld/p/14601347.html
 
-[COCI2014-2015#1]Kamp
 
-[APIO2014]连珠线
+#### [$P3647$ $APIO2014$ 连珠线](https://www.luogu.com.cn/problem/P3647)
 
-POJ3585 Accumulation Degree
 
-CF708C Centroids
+#### [$POJ3585$ $Accumulation$ $Degree$](http://poj.org/problem?id=3585)
+https://blog.csdn.net/qq_34493840/article/details/90575293
 
-Eg3: AT Educational DP Contest V-Subtree
+
+#### [$CF708C$ $Centroids$](https://www.luogu.com.cn/problem/CF708C)
+https://www.cnblogs.com/DongPD/p/17498336.html
+
+
+#### [Eg3: AT Educational DP Contest V-Subtree](https://dmoj.ca/problem/dpv)
 
 #### [$AcWing$ $1073$. 树的中心](https://www.cnblogs.com/littlehb/p/15786805.html)