System tests docs: Add link to publication

Author: MakisH

tools/tests/README.md

@@ -8,6 +8,8 @@ summary: "Test complete simulations combining preCICE components of specific ver
 
 The tutorials repository hosts cases that need multiple components from the preCICE ecosystem to run. This directory provides tools that can automatically run complete simulations, using different versions of each component, and compare the results to references. While the main purpose is to run complete tests in the continuous integration workflows of preCICE, you can also run these tests on your laptop.
 
+Read more about the system tests in the publication [System Regression Tests for the preCICE Coupling Ecosystem](https://doi.org/10.14279/eceasst.v83.2614).
+
 ## Running the system tests
 
 The main workflow for the user is executing the `systemtests.py` script. Depending on the options given to the script, it reads in the respective metadata files and generates `docker-compose.yaml` files that can start a fully-defined coupled simulation.