diff --git a/development-updates.md b/development-updates.md
index 60107b2..97c672d 100644
--- a/development-updates.md
+++ b/development-updates.md
@@ -148,7 +148,7 @@ The actual project development is the main part of the program. Post your regula
 | [ghili](https://github.com/ghiliweld)                        | [Update 6](https://hackmd.io/@ghili/HJI5KJQ_A)                  | [Update 7](https://hackmd.io/@ghili/HkBl2pGY0)                  | [Update 8](https://hackmd.io/@ghili/B1dMYUBYR)                  |                                                                 |                                                                   |                                                                    |                                                                   |         |         |         |         |         |         |         |         |           |
 | [Glory Agatevure](https://github.com/gconnect)               | [Update 6](https://hackmd.io/@gconnect/Sy9n-IKwA)               | [Update 7](https://hackmd.io/@gconnect/ryNMVbXY0)               | [Update 8](https://hackmd.io/@gconnect/r1wHFvpY0)               | [Update 9](https://hackmd.io/@gconnect/r1Q_zrI5A)               | [Update 10](https://hackmd.io/@gconnect/SyZOYSlsA)                | [Update 11](https://hackmd.io/@gconnect/rkSsQBKi0)                 | [Update 12](https://hackmd.io/@gconnect/rJq9H2G2A)                |         |         |         |         |         |         |         |         |           |
 | [Hamid Bateni](https://github.com/irnb)                      | [Update 6](https://hackmd.io/@irnb/epf_week6)                   |                                                                 |                                                                 |                                                                 |                                                                   | [Pivot Update](https://hackmd.io/@irnb/epf_week11)                 |                                                                   |         |         |         |         |         |         |         |         |           |
-| [Hangleang](https://github.com/hangleang)                    | [Update 6](https://hackmd.io/@hangleang/epf5-week6)             |                                                                 | [Update 7&8](https://hackmd.io/@hangleang/epf5-week7n8)         | [Update 9](https://hackmd.io/@hangleang/epf5-week9)             | [Update 10](https://hackmd.io/@hangleang/epf5-week10)             | [Update 11](https://hackmd.io/@hangleang/epf5-week11)              | [Update 12](https://hackmd.io/@hangleang/epf5-week12)             |         |         |         |         |         |         |         |         |           |
+| [Hangleang](https://github.com/hangleang)                    | [Update 6](https://hackmd.io/@hangleang/epf5-week6)             |                                                                 | [Update 7&8](https://hackmd.io/@hangleang/epf5-week7n8)         | [Update 9](https://hackmd.io/@hangleang/epf5-week9)             | [Update 10](https://hackmd.io/@hangleang/epf5-week10)             | [Update 11](https://hackmd.io/@hangleang/epf5-week11)              | [Update 12](https://hackmd.io/@hangleang/epf5-week12)             | [Update 13](https://hackmd.io/@hangleang/epf5-week13)             |         |         |         |         |         |         |         |           |
 | [Hopinheimer](https://github.com/hopinheimer)                |                                                                 | [Update 7](https://hackmd.io/@hopin232/S1VgE2j_A)               | [Update 8](https://hackmd.io/@hopin232/BJrO3ITFA)               |                                                                 |                                                                   | [Week 11](https://hackmd.io/@hopin232/Skm863wjA)                   |                                                                   |         |         |         |         |         |         |         |         |           |
 | [Ifeoluwa Oderinde](https://github.com/owanikin)             |                                                                 |                                                                 |                                                                 |                                                                 |                                                                   | [Update 11](https://hackmd.io/@ZpBFaS-NSO-5Xkdm4jwolg/BkjyzCKiC)   |                                                                   |         |         |         |         |         |         |         |         |           |
 | [Jihoon Song](https://github.com/jihoonsong)                 | [Update 6](https://hackmd.io/@jihoonsong/SJMKLaoOA)             | [Update 7](https://hackmd.io/@jihoonsong/HypZY0EKA)             | [Update 8](https://hackmd.io/@jihoonsong/rkag8fRYC)             | [Update 9](https://hackmd.io/@jihoonsong/SkAFlxD5R)             | [Update 10 & 11](https://hackmd.io/@jihoonsong/SkXyL5YoR)         |                                                                    |                                                                   |         |         |         |         |         |         |         |         |           |
diff --git a/notes/hangleang.md b/notes/hangleang.md
index fe67154..048bd13 100644
--- a/notes/hangleang.md
+++ b/notes/hangleang.md
@@ -20,3 +20,8 @@ Lastly, thanks to @ghili. I'm permissionlessly fork your note, cause we have som
 - [peerdas-devnet-1 specs](https://notes.ethereum.org/@ethpandaops/peerdas-devnet-1) by EthPandaOps Team
 - [libp2p-pubsub Peer Discovery with Kademlia DHT](https://medium.com/rahasak/libp2p-pubsub-peer-discovery-with-kademlia-dht-c8b131550ac7)
 - [DAS and Danksharding](https://a16zcrypto.com/posts/article/an-overview-of-danksharding-and-a-proposal-for-improvement-of-das) 
+
+### Tools
+- [ENR Viewer](https://enr-viewer.com/): decoding ENR to inspect `csc` field (custody subnet count), maintained by ChainSafe
+- [PeerDAS Custody](https://jimmygchen.github.io/peerdas-custody/): compute custody subnets and columns from node ID or peer ID, maintained by [jimmygchen](https://github.com/jimmygchen) from Lighthouse
+    - [My fork with config updates](https://hangleang.github.io/peerdas-custody/)