diff --git a/content/3.defense-systems/paris.md b/content/3.defense-systems/paris.md
index 0ab10f90dd98dc181d78da1a0f7340b866e6b129..ab1578d2baffaa765adfafec62e830a30864fa3c 100644
--- a/content/3.defense-systems/paris.md
+++ b/content/3.defense-systems/paris.md
@@ -19,11 +19,11 @@ relevantAbstracts:
 
 ## Description
 
-PARIS (for Phage Anti-Restriction-Induced System) is a novel anti-phage system. It comprises an ATPase associated with a DUF4435 protein, which can be found either as a two-gene cassette or a single-gene fusion (1).
+PARIS (for Phage Anti-Restriction-Induced System) is a novel anti-phage system. It comprises an ATPase associated with a DUF4435 protein, which can be found either as a two-gene cassette or a single-gene fusion :ref{doi=10.1016/j.chom.2022.02.018}.
 
 ## Molecular mechanisms
 
-This system relies on an unknown [Abortive infection](/general-concepts/abortive-infection) mechanism to trigger growth arrest upon sensing a phage-encoded protein (Ocr). Interestingly, the Ocr protein has been found to inhibit R-M systems and BREX systems, making PARIS a suitable defense mechanism against RM resistant and/or BREX resistant phages (1, 2, 3). 
+This system relies on an unknown [Abortive infection](/general-concepts/abortive-infection) mechanism to trigger growth arrest upon sensing a phage-encoded protein (Ocr). Interestingly, the Ocr protein has been found to inhibit R-M systems and BREX systems, making PARIS a suitable defense mechanism against RM resistant and/or BREX resistant phages :ref{doi=0.1016/j.chom.2022.02.018,10.1093/nar/gkaa510,10.1007/BF01036001}. 
 
 ## Example of genomic structure