diff --git a/google-alternatives.md b/google-alternatives.md
index 52c7537b5..f3be8783b 100644
--- a/google-alternatives.md
+++ b/google-alternatives.md
@@ -1,6 +1,7 @@
 # Google Alternatives
 
 - [[go]] https://kiramclean.com/blog/what-i-use-now-instead-of-google/
+  - Seen on [[hn]]: https://news.ycombinator.com/item?id=25654222
   - [[GMail]] → [[ProtonMail]]
   - [[Chrome]] → [[Firefox developer edition]]
   - [[Google search]] → [[DuckDuckGo]]
@@ -14,6 +15,7 @@
 
 [//begin]: # "Autogenerated link references for markdown compatibility"
 [go]: go "Go"
+[hn]: hn "HN"
 [GMail]: gmail "Gmail"
 [Chrome]: chrome "Chrome"
 [//end]: # "Autogenerated link references"
\ No newline at end of file
diff --git a/journal/2021-01-06.md b/journal/2021-01-06.md
index f207cdddd..aaea670ce 100644
--- a/journal/2021-01-06.md
+++ b/journal/2021-01-06.md
@@ -1,4 +1,12 @@
 # 2021-01-06
 
 - [[ligeti]]
-- [[google alternatives]]
\ No newline at end of file
+- [[google alternatives]]
+- Received [[a new kind of science]] on the mail.
+- [[max tegmark]] [[mathematical universe]]
+
+[//begin]: # "Autogenerated link references for markdown compatibility"
+[ligeti]: ../ligeti "Ligeti"
+[google alternatives]: ../google-alternatives "Google Alternatives"
+[a new kind of science]: ../a-new-kind-of-science "A New Kind of Science"
+[//end]: # "Autogenerated link references"
\ No newline at end of file
diff --git a/mathematical-universe.md b/mathematical-universe.md
new file mode 100644
index 000000000..a9ebbd909
--- /dev/null
+++ b/mathematical-universe.md
@@ -0,0 +1,9 @@
+# Mathematical Universe
+
+- [[pull]] [[mathematical universe hypothesis]]
+- [[by]] [[max tegmark]]
+
+
+[//begin]: # "Autogenerated link references for markdown compatibility"
+[pull]: pull "Pull"
+[//end]: # "Autogenerated link references"
\ No newline at end of file