diff --git a/journal/2021-03-26.md b/journal/2021-03-26.md
index 048a4db1b..b1525b9c9 100644
--- a/journal/2021-03-26.md
+++ b/journal/2021-03-26.md
@@ -8,6 +8,7 @@
     - [[goodreads bridge]]
 - [[angelus]]    
 - [[wittgenstein plays chess]]
+- [[tree structures]]
 - [[push]] [[etherpad]]
   - [[etherpad plugins]]
   - [[restore etherpad revision]]
diff --git a/tree-structures.md b/tree-structures.md
new file mode 100644
index 000000000..2df761070
--- /dev/null
+++ b/tree-structures.md
@@ -0,0 +1,4 @@
+# tree structures
+
+- https://twitter.com/flancian/status/1375493771786326016
+