diff --git a/an analysis of the role of invariant patterns.md b/an analysis of the role of invariant patterns.md
index 5a4caf499..58929141d 100644
--- a/an analysis of the role of invariant patterns.md	
+++ b/an analysis of the role of invariant patterns.md	
@@ -1,4 +1,5 @@
 - a [[paper]]
 	- about [[invariant patterns]] in [[a pattern language]] 
 	- [[go]] https://journals.sagepub.com/doi/full/10.1177/2399808318761396
+		- [[pdf]] https://journals.sagepub.com/doi/pdf/10.1177/2399808318761396
 		- "despite its popularity, the structure of _A Pattern Language_ remains poorly understood. In response to this situation, this paper uses graph theory to examine Alexander’s language including the entire set of 253 patterns and over 1800 relationships between them."
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