diff --git a/books/sociology/secrecy.md b/books/sociology/secrecy.md
index 3cf49bac91f9ce62666a797b10e4542fed7e0294..693106a06e693554ba2d7913587ed3fecb3cff90 100644
--- a/books/sociology/secrecy.md
+++ b/books/sociology/secrecy.md
@@ -1,6 +1,9 @@
 [[!meta title="The Sociology of Secrecy and of Secret Societies"]]
 
-By Georg Simmel.
+By Georg Simmel:
+
+* [Full text](https://brocku.ca/MeadProject/Simmel/Simmel_1906.html).
+* [Comments and references](https://en.wikipedia.org/wiki/Sociological_aspects_of_secrecy).
 
 ## Excerpts